Experiment 6.4 Aim: To study the effect of the type of electrode on the selection of ion to be discharged at the electrode Problem statement: How does the type of electrode affect the selection of ion to be discharged at the anode? Hypotheses: 1. If carbon electrodes are used during the electrolysis of copper(II) sulphate solution, CuSO4, then the hydroxide ion, OH– , is selected to be discharged at the anode. 2. If copper electrodes are used during the electrolysis of copper(II) sulphate solution, CuSO4, then the copper(II) ion, Cu2+, is formed at the anode. Variables: (a) manipulated : Type of electrode (carbon or copper) (b) responding : Product of electrolysis at the anode (c) constant : Type and concentration of electrolyte Materials: 0.1 mol dm–3 copper(II) sulphate solution, CuSO4 and wooden splinter Apparatus: Battery, carbon electrodes, copper electrodes, connecting wires with crocodile clips, electrolytic cell, ammeter, test tubes and switch Procedure: 1. Prepare the apparatus set-up with an electrolytic cell half-filled with 0.1 mol dm–3 copper(II) sulphate solution, CuSO4. 2. Fill completely a test tube with 0.1 mol dm–3 copper(II) sulphate solution, CuSO4 and then invert the test tube at the anode (Figure 6.11). Figure 6.11 Battery Ammeter Switch A Copper(II) sulphate solution, CuSO4 Carbon electrodes + + – – (b) Cathode (negative electrode) (i) Attracts positive ions, namely silver ions and hydrogen ions (ii) Silver ions are selected to be discharged because the silver ion is less electropositive compared to the hydrogen ion (iii) Silver is deposited at the cathode (c) Anode (positive electrode) (i) Attracts negative ions, namely nitrate ions and hydroxide ions (ii) Hydroxide ions are selected to be discharged because the hydroxide ion is less electronegative compared to the nitrate ion (iii) Oxygen gas is produced at the anode (d) The concentration of silver ions in the electrolyte decreases because the silver ions from the electrolyte are discharged to become silver atoms and deposited at the cathode. 190 6.1.3
Application of Electrolysis in Industries Examples of applications of electrolysis in industries include: (a) Extraction of metals In Form 3, you have studied the position of metals in the reactivity series of metal and methods of metal extraction from their ores. Metals like potassium, sodium, calcium, magnesium and aluminium are extracted from their molten ores or salts through electrolysis. (b) Purification of metals In the purification of metal, the impure metal is used as the anode while the pure metal is used as the cathode. During electrolysis, the metal at the anode will dissolve into the electrolyte to form ions. These ions will move to the cathode to be discharged and deposited at the cathode as pure metal. (c) Electroplating of metals In the process of electroplating a metal, gold, platinum and silver are electroplated on other metals to make the metal look more attractive and to withstand corrosion. (d) Wastewater treatment using electrocoagulation Electrocoagulation is an innovative technique to treat wastewater (Figure 6.12). Electrocoagulation applies two processes, namely electrolysis and coagulation. 3. Turn on the switch for 15 minutes. Observe and record the changes that occur at the anode. 4. Test any gas released using a glowing wooden splinter. 5. Observe and record the result of the gas test. 6. Repeat steps 1 to 4 by replacing the carbon electrodes with copper electrodes. Observation: Type of electrode Glowing wooden splinter test at anode Carbon electrode Copper electrode Conclusion: Are the hypotheses accepted? What is the conclusion for this experiment? Questions: 1. Name the ions present in the electrolyte during electrolysis. 2. Name the ions selected to be discharged or the ions produced at the anode for the following types of electrodes: (a) carbon electrode (b) copper electrode 191 Chapter 6 Electrochemistry 6.1.3 6.1.4
A simple chemical cell is made up of two different metals immersed in an electrolyte and connected to an external circuit with connecting wires (Figure 6.13). Observe the simple chemical cell which is made up of magnesium and copper electrodes in Figure 6.14 and the electrochemical series in Figure 6.15. 6.2 Chemical Cell Voltmeter V Copper(II) sulphate solution, CuSO4 Magnesium Copper – + Figure 6.13 Example of a simple chemical cell Formative Practice 6.1 • Electrolysis ➊ At the anode, a metal electrode such as aluminium ionises in the electrolyte to produce positively charged aluminium ions, Al3+. ➋ At the cathode, hydrogen ions, H+ are selected to be discharged to form hydrogen gas. Hydrogen gas bubbles are released from the cathode and rise to the water surface. • Coagulation ➌ Coagulation occurs when aluminium ions, Al3+, hydroxide ions, OH– and pollutants in the wastewater combine to produce coagulants known as floc. ➍ Floc, trapped in hydrogen gas bubbles released from the cathode, are brought up to the water surface. ➎ The remaining flocs sinks and accumulates at the base. 1. Draw and label the structures of an electrolytic cell. 2. Describe the movement of ions to electrodes during electrolysis. 3. Give four examples of applications of electrolysis in industries. Figure 6.12 Electrocoagulation Hydrogen gas bubble Pollutant Cathode such as carbon Floating floc H2 OH– e– e– Al3+ Al3+ OH– H+ H+ 1 3 5 2 4 Sedimented floc Wastewater Metal anode such as aluminium sheet Floc Floc floating in hydrogen gas bubble 192 6.1.4 6.2.1
• Magnesium which donates electrons forms magnesium ions and dissolves in the electrolyte (copper(II) sulphate solution). • Magnesium acts as the negative terminal of the chemical cell. • The released electrons will flow through the external circuit from magnesium to copper which acts as the positive terminal of the chemical cell. • The flow of electrons from the negative terminal to the positive terminal through the external circuit will produce electrical energy. • Conversion of energy which occurs in the chemical cell is from chemical energy to electrical energy. • Electrons from magnesium are received by the copper(II) ion from the electrolyte and not by the hydrogen ion because the copper(II) ion is less electropositive than the hydrogen ion. • Solid copper is formed and deposited on the copper strip. • Copper acts as the positive terminal of the chemical cell. Figure 6.15 Electrochemical series showing arrangement of ions in order of electropositivity Figure 6.16 Chemical reactions in a chemical cell with different metal electrodes Increasing electropositivity ION Potassium ion, K+ Sodium ion, Na+ Calcium ion, Ca2+ Magnesium ion, Mg2+ Aluminium ion, Al3+ Zinc ion, Zn2+ Iron(II) ion, Fe2+ Tin ion, Sn2+ Lead(II) ion, Pb2+ Hydrogen ion, H+ Copper(II) ion, Cu2+ Silver ion, Ag+ Figure 6.14 Simple chemical cell Copper(II) sulphate solution, CuSO4 Copper Voltmeter V Magnesium – + By referring to the simple chemical cell in Figure 6.14, magnesium becomes the negative terminal and copper becomes the positive terminal. This is because magnesium is more electropositive than copper (Figure 6.15). Magnesium is more likely to donate electrons compared to copper. Flow of Voltmeter electrons Flow of electrons Copper(II) sulphate solution, CuSO4 Copper V Magnesium – + 193 Chapter 6 Electrochemistry 6.2.1
Activity 6.2 Application of Chemical Cell Concept in Generating Electrical Energy from a Variety of Sources Can fruits or other parts of a plant and seawater be used to generate electrical energy? Let us carry out Activity 6.3 to generate ideas on how the concept of chemical cell can be applied to generate electrical energy from a variety of sources. To build a simple chemical cell Materials Sandpaper, two magnesium ribbons, two copper strips and 1.0 mol dm–3 sodium chloride solution, NaCl Apparatus Measuring cylinder, beaker, connecting wires with crocodile clips and voltmeter Instructions 1. Clean two magnesium ribbons and two copper strips with sandpaper. 2. Measure and pour 150 cm3 of 1.0 mol dm–3 sodium chloride solution, NaCl into a clean beaker using a measuring cylinder. 3. Immerse a magnesium ribbon and a copper strip into the sodium chloride solution, NaCl, in the beaker. 4. Connect the magnesium ribbon, copper strip and voltmeter with connecting wires (Figure 6.17). 5. Turn on the switch. Observe and record the voltmeter reading. 6. Repeat steps 1 to 5 by replacing the magnesium ribbon and copper strip with a pair of magnesium ribbons and a pair of copper strips. Result Pair of metals Voltmeter reading (V) Magnesium – copper Magnesium – magnesium Copper – copper 21 Century Skills st • TPS • Inquiry-based activity Voltmeter Switch V Sodium chloride solution, NaCl Copper strip Magnesium ribbon – + Figure 6.17 Simple chemical cell 194 6.2.1 6.2.2
Activity 6.3 To generate electrical energy from fruits or other plant parts and seawater Instructions 1. Carry out this activity in groups to generate ideas on how the concept of chemical cell can be applied to generate electrical energy from a variety of sources. Study the following statement: The generation of electrical energy can be obtained from a variety of sources. For example, a simple chemical cell is a device which can convert chemical energy into electrical energy. 2. Plan and carry out a project based on the STEM approach. Build a simple chemical cell which can convert chemical energy into electrical energy from various sources such as fruits or other plant parts and seawater. 3. Gather and discuss information or ways to construct a simple chemical cell from fruits or other plant parts and seawater from the following websites: Related websites (a) Electrical energy produced from fruits http://buku-teks.com/sc5195a (b) Electrical energy produced from vegetables http://buku-teks.com/sc5195b 4. Present your simple chemical cell design to the class. 21 Century Skills st • TPS, STEM • STEM projectbased activity Formative Practice 6.2 1. What is a simple chemical cell? 2. Draw and label a simple chemical cell. 3. How does the position of an ion in the electrochemical series determine the positive terminal and the negative terminal in a simple chemical cell? 195 Chapter 6 Electrochemistry 6.2.2
Summary Summary S at affected by factors Electrochemistry Electrolytic cell Chemical cell Anode, cathode, anion, cation, electrolyte and electrical source Electrolyte and two different types of metals Metal rod, electrolyte Electrical energy to chemical energy Chemical energy to electrical energy Electrolysis Chemical changes that occur in cell Products of electrolysis Position of ions in the electrochemical series, concentration of electrolyte and types of electrode Extraction of metal, purification of metal, electroplating of metal, treatment of wastewater through electrocoagulation Applications in industries Study in the field of chemistry on the relationship between chemical and electrical phenomena 196
6.1 Electrolytic Cell Understand electrolysis. Carry out experiments to study electrolysis of ionic compounds in various conditions. Carry out experiments to study the factors affecting the products in electrolysis. Communicate about the application of electrolysis in industries. 6.2 Chemical Cell Explain the energy change in a simple chemical cell. Generate ideas on the application of the chemical cell concept in generating electricity from a variety of sources. Self-Reflection Self-Reflection After studying this chapter, you are able to: Summative Practice 6 Summative Practice 6 Quiz http://bukuteks.com/ sc5197 Answer the following questions: 1. Figure 1 shows an apparatus set-up to study the electrolysis of an aqueous copper(II) sulphate solution, CuSO4 using different electrodes as shown in electrolytic cell P and electrolytic cell Q. Aqueous copper(II) sulphate solution, CuSO4 Carbon Copper + – + – Electrolytic cell P Electrolytic cell Q Figure 1 (a) State the meaning of electrolysis. (b) State all the ions present in the aqueous copper(II) sulphate solution. (c) Name the ions discharged at the anode and cathode for the following electrolytic cells: (i) electrolytic cell P (ii) electrolytic cell Q at anode: at anode: at cathode: at cathode: (d) Name one example of the application of electrolysis in industries which applies the electrolysis concept of electrolytic cell Q. 197 Chapter 6 Electrochemistry
2. Figure 2 shows an apparatus set-up to study the electrolysis of aqueous sodium nitrate solution, NaNO3, using carbon electrodes labelled P and Q. Electrode P Battery Ammeter A Aqueous sodium nitrate solution, NaNO3 Electrode Q + + – – Figure 2 (a) (i) State all the cations present in the electrolyte. (ii) State all the anions present in the electrolyte. (b) Which electrode acts as the anode? (c) Name the ion chosen to be discharged at: (i) electrode P: (ii) electrode Q: (d) Explain your answer in 2(c)(ii) based on the selection of ion to be discharged. 3. Rohani found a rusted iron nail. Using your knowledge of electrolysis, describe a simple way to prevent the rusting of the iron nail. 4. You are given three potatoes, three iron nails, three copper rods, light bulb and connecting wires with crocodile clips. Using these materials, design a simple chemical cell with the following features: (a) simple chemical cell that can light up a light bulb with maximum brightness. (b) simple chemical cell that can last the longest when lighting up a light bulb. Enrichment Practice Enrichment Practice 198
Energy and Sustainability of Life 3 HEME Click@Web Biggest telescope in the world http://buku-teks.com/sc5199a Look through a ‘live’ telescope http://buku-teks.com/sc5199b The drone is a scientific invention that is becoming increasingly popular. Name one physics principle applied in the flight of a drone. The Swedish 1-m Solar Telescope in La Palma, Spain has a convex lens as the objective lens with a diameter of approximately 1.10 m. Why do astronomers need to observe outer space through the telescope all the time, that is, 24 hours a day? 199
LIGHT AND OPTICS Let’s study L t'PSNBUJPOPGJNBHFTCZMFOTFT t0QUJDBMJOTUSVNFOUT 7 CHAPTER Name the types of lenses used to correct long-sightedness and short-sightedness. State one advantage of liquid lens compared to glass lens. Besides thickness, name one factor which affects the focal length of lens. 200
Handphone without camera Smartphone with five cameras Camera quality is normally related to the type or quality of lens attached to the camera. This is because the image in the camera is formed by the lens. Besides transparent glass and plastic, any transparent material including water can be used to make lenses. The concept of liquid lens is shown in the photograph below. Nowadays, the use of lenses in optical instruments is expanding. For example, the telephone which was originally an audio communication device has been developed into a smartphone which can function as an audio-visual communication device using a camera to take photographs and videos. r $POWFYMFOT r $POWFSHJOHMFOT r $PODBWFMFOT r %JWFSHJOHMFOT r 'PDBMQPJOU r 'PDBMMFOHUI r 3BZEJBHSBN r 1SJODJQBMBYJT r 0QUJDBMDFOUSF r 0CKFDUEJTUBODF r *NBHFEJTUBODF r .JDSPTDPQF r .BHOJGZJOHQPXFS r 5FMFTDPQF r /PSNBMBEKVTUNFOU rCCTV r -FOTFTJOPQUJDBM JOTUSVNFOUT Concept of liquid lens Science Bulletin Science Bulletin Keywords 201
Biconvex Planoconvex Convex meniscus Biconcave Planoconcave Concave meniscus Concave lens Convex lens 7.1 Formation of Images by Lenses Convex Lens and Concave Lens A lens is a transparent medium such as glass which has one or two curved surfaces. Lenses are divided into two types, convex lens and concave lens as shown in Figure 7.1. Figure 7.1 Convex lens and concave lens Figure 7.2 shows the path of light rays before and after passing through a convex lens and a concave lens. What happens to the light rays after passing through these lenses? Figure 7.2 Refraction of light rays after passing through a convex lens and a concave lens Based on Figure 7.2, light rays converge after passing through a convex lens while light rays diverge after passing through a concave lens. Therefore, a convex lens is known as a converging lens while a concave lens is known as a diverging lens. 202 7.1.1
(a) Convex lens (b) Concave lens Focal length, f Concave lens Focal length, f Focal point, F Convex lens Principal axis Principal axis Focal point F For convex lenses, the focal point, F is a point where light rays parallel to the principal axis converge after passing through the convex lens (Figure 7.3(a)). Figure 7.3 Focal point and focal length for convex lens and concave lens When light rays which diverge after passing through a concave lens are extrapolated backwards, the light rays will intersect at a point. This point is the focal point, F for the concave lens (Figure 7.3(b)). Let us carry out Activity 7.1 to study some properties of convex lenses and concave lenses using an Optical Ray Kit. Use the Optical Ray Kit to: (a) show the convex lens as a converging lens and the concave lens as a diverging lens (b) determine the focal points of convex lenses and concave lenses Materials White paper (sized 86 cm × 86 cm) Apparatus Optical Ray Kit containing ray box, cylindrical biconvex lens, cylindrical biconcave lens, triple slit plate, ruler and pencil Note: This activity is best suited to be carried out in the dark. Activity 7.1 21 Century Skills st • TPS • Inquiry-based activity 7.1.1 Chapter 7 Light and Optics 203
Instructions Path of parallel rays White paper Cylindrical biconvex lens Triple slit Ray box plate Figure 7.4 1. Prepare the apparatus set-up shown in Figure 7.4. 2. Trace the shape of the convex lens onto a piece of white paper using a pencil. Mark the centre point of the convex lens, that is the optical centre, O on the tracing of the convex lens. 3. Direct three parallel light rays from the ray box in the direction of the convex lens. Observe the path of light rays before and after passing through the convex lens. 4. Make two marks, one near to the lens and another far from the lens, on each path of the light rays before and after passing through the convex lens. Remove the convex lens from the white paper. 5. Draw a straight line using a pencil and ruler to connect the two marks on each path of the light rays before and after passing through the convex lens (Figure 7.3(a)). 6. Mark the point of intersection of the three light rays as the focal point, F for the convex lens. 7. Repeat steps 1 to 5 by replacing the convex lens with a concave lens. 8. Extrapolate the light rays which diverge after passing through the concave lens backwards until a point of intersection (Figure 7.3(b)). 9. Mark the point of intersection of the three light rays as the focal point, F for the concave lens. Questions 1. Why is it more suitable for this activity to be carried out in the dark? 2. What happens to light rays after passing through the following lenses? (a) Convex lens (b) Concave lens 3. Describe the observations made in this activity that show the following properties of lenses: (a) convex lens as a converging lens (b) concave lens as a diverging lens Video Eduweb TV: Physics – lenses http://buku-teks. com/sc5204 (Medium: bahasa Melayu) 204 7.1.1
Determining the Focal Length of a Convex Lens Before carrying out Activity 7.2, let us understand optical terms (Table 7.1). (a) Convex lens (b) Concave lens Figure 7.5 Convex lens and concave lens Table 7.1 Optical terms and their explanations Optical term Explanation Optical centre, O Point at the centre of the lens. Light rays which pass through the optical centre do not refract. Principal axis A straight line which passes through the optical centre of a lens and the focal point, F. Axis of lens Straight line which passes through the optical centre and is perpendicular to the principal axis. Focal point, F (refer to Figure 7.3) • For convex lens, the focal point, F is a point on the principal axis, where light rays parallel to the principal axis converge after passing through the lens. • For concave lens, the focal point, F is a point on the principal axis, where light rays parallel to the principal axis appear to diverge from it after passing through the lens. Focal length, ƒ The distance between the focal point, F and the optical centre. Object distance, u The distance between the object and the optical centre. Image distance, ν The distance between the image and the optical centre. 2F F F 2F Object Image O f f u v Axis of lens Principal axis 2F F F 2F Object Image f f v u Principal axis O Axis of lens Chapter 7 Light and Optics 7.1.2 205
Ray Diagrams to Determine the Characteristics of Images Formed by Convex Lenses and Concave Lenses Besides carrying out activities using appropriate apparatus such as in Activity 7.2, the position and characteristics of images formed by convex lenses and concave lenses can be determined using ray diagrams. Study and understand Table 7.2 which explains the method of drawing ray diagrams by drawing two principal light rays to determine the characteristics of the images formed by convex lenses and concave lenses. Video Steps to draw ray diagrams http://buku-teks. com/sc5206 (Medium: bahasa Melayu) To determine the focal length of a convex lens using a distant object Materials Convex lens, lens holder, white screen and metre rule Instructions 1. Prepare the apparatus set-up as shown in Figure 7.7. 2. Position the convex lens towards a distant object seen through an open window. 3. Adjust the position of the white screen until a sharp image of the distant object is formed on the screen. 4. Measure and record the distance between the centre of the convex lens and the screen, that is the focal length, f of the convex lens using a metre rule. Questions 1. Why are laboratory objects not used to determine the focal length of a convex lens in this activity? 2. State the characteristics of the image formed on the white screen. 3. If the convex lens in this activity is replaced with a concave lens, can the focal length of the concave lens be estimated? Explain your answer. Let us carry out Activity 7.2 to determine the focal length of a convex lens using a distant object by applying the concept that light rays from a distant object are parallel (Figure 7.6). Figure 7.6 Parallel light rays from a distant object o F f O Activity 7.2 21 Century Skills st • TPS • Inquiry-based activity Laboratory window Lens holder Convex lens White screen Figure 7.7 206 7.1.2 7.1.3
Table 7.2 Method for drawing ray diagrams Convex lens 1 A light ray parallel to the principal axis refracts and passes through the focal point, F. 2 A light ray heading towards the optical centre continues in a straight line through the optical centre without refracting. Concave lens 1 A light ray parallel to the principal axis refracts and appears to come from the focal point, F. 2 A light ray heading towards the optical centre continues in a straight line through the optical centre without refracting. Object F F 1 1 Object F F 1 1 Object Real image F F 1 1 2 2 Virtual image Object F F 1 1 2 2 7.1.3 207 Chapter 7 Light and Optics
Tables 7.3 and 7.4 show the positions of object, ray diagrams, positions of image and characteristics of images for convex lens and concave lens, respectively. Table 7.3 Ray diagrams to determine the characteristics of images formed by a convex lens Position of object Ray diagram Position of image Characteristics of image Object is further than 2F Image is between F and 2F • Real • Inverted • Diminished Object is at 2F Image is at 2F • Real • Inverted • Same size as object Object is between F and 2F Image is further than 2F • Real • Inverted • Magnified Object is at F Image is at infinity • Virtual • Upright • Magnified Object is between F and optical centre (Used as a magnifying glass) Image distance is further than F • Virtual • Upright • Magnified 2F F F 2F 2F F F 2F 2F F F 2F F F Object Object Object Object Image Image Image 2F F F 2F Object Image 208 7.1.3
Table 7.4 Ray diagrams to determine the characteristics of images formed by a concave lens Position of object Ray diagram Position of image Characteristics of image Object is further than 2F Between optical centre and focal point • Virtual • Upright • Diminished Object is between F and optical centre Between optical centre and focal point • Virtual • Upright • Diminished Note: The characteristics of images formed by concave lenses for any object distance are: • virtual • upright • diminished • positioned between the object and the concave lens 1. Name the type of lens found in the human eye. 2. Figure 1 shows two types of lenses. Figure 1 (a) Name the following types of lenses: (i) Lens X (ii) Lens Y (b) (i) Which lens functions as a diverging lens? (ii) Which lens functions as a converging lens? (c) Mark the focal point of lenses X and Y with the letter F. 3. How is the convex lens used as a magnifying glass? Lens X Lens Y 2F F F 2F 2F F F 2F Object Object Image Image Formative Practice 7.1 BRAIN TEASER Reinforcement practice http://buku-teks.com/sc5207 7.1.3 209 Chapter 7 Light and Optics
Photograph 7.1 shows three optical instruments. Describe the characteristics of the final image formed by these three optical instruments. Formation of the Final Image by a Microscope Study the two ray diagrams in Figure 7.8. Figure 7.8 Ray diagrams for the images formed by the objective lens and eyepiece of a microscope 7.2 Optical Instruments (a) Object is between F and 2F Image position: Image is further than 2F Image characteristics: • Real • Inverted • Magnified (b) Object is between F and the optical centre, O Image position: Image is further than F Image characteristics: • Virtual • Upright • Magnified 2F F Object F 2F Objective lens Image O F F Eyepiece Object Image O Magnifying glass Microscope Astronomical telescope Photograph 7.1 Optical instruments The function of optical instruments is normally related to the type of image, whether real or virtual, and the size of image formed by the lens. The ray diagrams in Tables 7.3 and 7.4 show that the image size formed by a lens depends on the position of the object from the centre of the lens. Scan Page 210 7.2.1
Example Based on your understanding of the two ray diagrams in Figure 7.8, the formation of the final image by a microscope is shown in Figure 7.9. Objective lens Eyepiece I Object Construction lines 2Fo Io First image, Virtual final image, Fo Fo Fe Fe Figure 7.9 Ray diagram showing the formation of the final image in a microscope Determining the Magnifying Power of a Microscope Magnifying power of microscope = Magnifying power of objective lens × Magnifying power of eyepiece Photograph 7.2 shows a microscope containing an eyepiece with a magnifying power of 4 times and an objective lens with a magnifying power of 40 times. Photograph 7.2 Calculate the magnifying power of the microscope. Solution Magnifying power of microscope = Magnifying power of objective lens × Magnifying power of eyepiece = 40 × 4 = 160 times Identify the objective lens and eyepiece of a microscope http://buku-teks. com/sc5211 Science g y gp ns with a power Chapter 7 Light and Optics 7.2.1 211
Formation of the Final Image by a Telescope Study the two ray diagrams in Figure 7.10. Figure 7.10 Ray diagrams for the images formed by the objective lens and eyepiece of a telescope Based on your understanding of the two ray diagrams in Figure 7.10, the formation of the final image by a telescope is shown in Figure 7.11. Objective lens Eyepiece fo Fo Fe Fo Fe fe Virtual final image at infinity, I First image, Io Parallel incident rays from a distant object Figure 7.11 Ray diagram showing the formation of the final image in a telescope In normal adjustment, the distance between the objective lens and eyepiece = ƒo + ƒe where ƒo = focal length of objective lens, ƒe = focal length of eyepiece so that the image can be viewed more comfortably. (a) Object at infinity Image position: Image at F Image characteristics: • Real • Inverted • Diminished (b) Object at F Image position: Image at infinity Image characteristics: • Virtual • Upright • Magnified F F Objective lens Image 2F F F 2F Eyepiece Object 212 7.2.1
Activity 7.3 To build a simple telescope model Materials Hollow paper cylinder and cellophane tape Apparatus Convex lens with focal length, ƒo ≥ 10 cm, convex lens with focal length, ƒe ≤ 2 cm, ruler, scissors or knife and pencil Instructions 1. Carry out the activity in groups. 2. Gather information from the Internet, print media and other electronic media about the following: (a) type, size and function of lenses used in a telescope (b) selection criteria for the objective lens and eyepiece of a telescope which can produce the clearest and brightest image (c) ray diagram to show the formation of image in a simple telescope 3. Discuss the information needed to complete the K-W-L Strategic Data Form as a guide to design and build your simple telescope. You can download and print the form from the website given below. 4. Sketch the design of the simple telescope. 5. Build your model according to the sketch made. 6. Comment on the effectiveness of the design and improve on the design produced. 7. Present your group’s telescope design and model. Questions 1. Why is the cylinder for the model telescope constructed from materials that are opaque and not transparent or translucent? 2. What is the distance between the objective lens and the eyepiece so that the final image can be seen more comfortably? 3. What is the name of the condition mentioned in question 2? Download K-W-L Strategic Data Form http://buku-teks.com/ sc5213 K-W-L Strategic Data Form What students already know, wish to know and will know (K-W-L chart) Already know (K – Know) Wish to know (W – Wonder) Will know (L – Learn) 21 Century Skills st • ICS, ISS, STEM • Innovative activity Chapter 7 Light and Optics 7.2.2 213
Digital single-lens reflex (DSLR) camera with two different lenses High-resolution closed-circuit television (CCTV) Spy camera in safety device Application of Lenses in Optical Instruments Photograph 7.3 Examples of optical instruments using lenses Technological advancements in the field of optics have enabled lenses used in optical instruments such as smartphones and closed-circuit television (CCTV) to be only several millimetres thick. Optical studies have succeeded in building flat lenses with a thickness of several microns only (1 micron = 0.001 mm). What are the effects of a flat lens on the size and thickness of smartphones? The focal length of the lens in the DSLR camera affects the field of vision. The shorter the focal length of the lens, the wider the field of vision as shown in Photograph 7.4. Photograph 7.4 Images formed using different focal lengths Camera image formed using a lens of focal length 70 mm from a distance of 15 m Camera image formed using a lens of focal length 24 mm from a distance of 15 m 214 7.2.3
Activity 7.4 To study the contributions of science and technology towards the invention of optical instruments that can help or overcome the limitations of human sight Instructions 1. Carry out the activity in groups. 2. Gather information from the Internet, print media and other electronic media on the following: (a) use of lenses in daily instruments such as cameras, smartphones, LCD projectors, spectacles, magnifying glasses and CCTV (b) the thickness and focal length of the camera lens of smartphones 3. Discuss the information gathered. 4. Present the outcome of your group discussion in the form of a multimedia presentation. 1. State the characteristics of the image formed by a magnifying glass. 2. Telescope X consists of an objective lens with a focal length of 30 cm and an eyepiece with a focal length of 5 cm. What is the separation distance between the objective lens and the eyepiece when telescope X is in normal adjustment? Photograph 7.5 shows a water lens placed under the sunlight. Photograph 7.5 Water lens Video A water lens can function as a magnifying glass http://buku-teks.com/sc5215 21 Century Skills st • ICS, ISS, TPS • Discussion Science Formative Practice 7.2 Chapter 7 Light and Optics 7.2.3 215
Summary Summary S by or or Convex lens Converging lens Diverging lens Ray diagrams Concave lens Microscope Characteristics of the final image: • virtual • magnified • inverted Characteristics of the final image: • virtual • magnified • inverted In normal adjustment, the distance between the objective lens and the eyepiece = ƒo + ƒe Telescope Camera, smartphone, LCD projector, spectacles, magnifying glass, CCTV Limitations of human sight to overcome Image formation Optical instruments Light and Optics Magnifying power of microscope = Magnifying power × Magnifying power of objective lens of eyepiece 216
Summative Practice 7 Summative Practice 7 7.1 Formation of Images by Lenses Describe convex lens as a converging lens and concave lens as a diverging lens. Determine the focal length of a convex lens using a distant object. Determine the characteristics of images formed by convex and concave lenses using ray diagrams. 7.2 Optical Instruments Describe the formation of the final image by telescopes and microscopes. Design and build a simple telescope. Communicate about the application of lenses in optical instruments. After studying this chapter, you are able to: Answer the following questions: 1. Draw ray diagrams which describe the following characteristics of lenses: (a) convex lens as a converging lens (b) concave lens as a diverging lens Self-Reflection Self-Reflection Quiz http://bukuteks.com/ sc5217 Chapter 7 Light and Optics 217
2. Figure 1 shows an object placed in front of a convex lens at a distance less than the focal length, ƒ. Figure 1 F F Object (a) Draw a ray diagram in Figure 1 to determine the image formed by the convex lens. (b) State the characteristics of the image formed by the convex lens in Figure 1. 3. (a) Why do smartphones have several cameras? (b) A student carried out an experiment to form a virtual image using a convex lens. Explain how the student formed the virtual image based on the apparatus set-up in Figure 2. PQR 2F F F 2F Figure 2 (i) Write the problem statement. (ii) State the position of the object (at P, Q or R). (iii) Using an arrow (↑) as the object, draw a ray diagram to show the formation and position of the image. Complete Figure 2 to obtain your answer. (iv) State two other characteristics of the image formed in 3(b)(iii). 218
Enrichment Practice A fly seen through a concave lens will appear smaller than its actual size. A fly seen through a convex lens will appear larger than its actual size. How does a lens make an object appear bigger or smaller? Lenses can be combined to make special optical instruments. Convex lens Concave lens This convex lens makes my eye appear bigger. Do you know the reason why? ave lens This concave lens makes my eye appear smaller. Do you know the reason why? Convex lens Magnified image of fly Concave lens Diminished image of fly 4. Optics is a scientific field that studies the properties of light, interactions between light and substances such as glass, human sight and instruments which use or detect light. Study and understand the contents of the poster in Figure 3. Figure 3 How effective is this poster in explaining the concept of image formation by lenses and optical instruments in the study of optics? Chapter 7 Light and Optics 219
FORCE AND PRESSURE Let’s study L t1SFTTVSFJOnVJET Do solids obey Pascal’s principle? Explain the problems that will arise in an aeroplane if its hydraulic system is damaged. 8 CHAPTER 220
r 1SFTTVSFJOáVJET r 1BTDBMTQSJODJQMF r &ODMPTFETZTUFN r )ZESBVMJDTZTUFN r )ZESBVMJDKBDLTZTUFN r )ZESBVMJDCSBLFTZTUFN r %JTDCSBLF r %SVNCSBLF r %FOUBMDIBJS r 7FOUVSJUVCF r 7FOUVSJFGGFDU r #FSOPVMMJTQSJODJQMF r -JGU r "FSPGPJMTIBQF r $SBOF Keywords Science Bulletin Science Bulletin Have you ever heard a loud hissing sound made by a heavy vehicle such as a tour bus or oil tanker when the vehicle stops? What is the system that operates in the heavy vehicle and produces this loud hissing sound? Light motor vehicles such as cars normally use hydraulic brakes. Heavy motor vehicles such as buses and lorries use air brakes that produce a larger frictional force to stop the motion of the vehicle. Nevertheless, both hydraulic brakes and air brakes use a system which applies Pascal’s principle. 221
Activity 8.1 8.1 Pressure in Fluids Concept of Pressure in Fluids in an Enclosed System Have you ever seen the device in Photograph 8.1? What is this device? This device operates based on the effect of pressure in hydraulic fluid in an enclosed system. An enclosed system is a physical system where matter cannot enter or leave the system. Name the fluid in this device. Based on Figure 8.1(a), water from the bottommost hole shoots out the furthest compared to water from the upper holes due to the pressure in the water. If force is applied to the water surface by compressing the closed plastic bottle, water from each hole will shoot further at an equal additional distance as shown in Figure 8.1(b). Pascal’s principle states that the transmission of pressure exerted on a fluid (liquid or gas) in an enclosed system is uniform throughout the fluid and in all directions. To explain Pascal’s principle using Pascal’s equipment Apparatus Round-bottom flask with fine pores and piston, and large beaker Figure 8.1 Uniform transmission of pressure in water in a closed plastic bottle (a) No additional pressure is exerted on the water (b) Additional pressure is exerted on the water y z x x + d y + d z + d Photograph 8.1 c fluid in an enclosed system. An r cannot enter or leave the system. 21 Century Skills st • TPS • Inquiry-based activity 222 8.1.1
Instructions 1. Carry out this activity in groups. 2. Prepare the apparatus set-up (Figure 8.2). 3. Pull the piston up until water fills the flask. 4. Remove the flask from the beaker and push the piston into the flask. 5. Observe and sketch the direction of water shooting out from the fine pores of the flask. Questions 1. How does water shoot out from the fine pores of the flask in all directions? Explain your answer. 2. Sketch the pattern of water shooting out from the fine pores of the flask in Figure 8.3. Pascal’s principle is commonly applied in daily life such as in the operation of the hydraulic system. Operating Principle of Hydraulic System The basic principle in a hydraulic system is the transmission of pressure in all directions based on Pascal’s principle. The hydraulic system is used to do heavy work such as producing a large output force to lift heavy loads. Study and understand the following example which shows the operation of the hydraulic system. The hydraulic system is made up of two cylindrical pistons of different surface areas. The fluid commonly used is water or oil (Figure 8.4). Water or oil is used because they do not have a fixed shape and cannot be compressed. Direction of push for piston Water Figure 8.3 Figure 8.4 Operation of hydraulic system 10 N Load Uniform transmission of pressure throughout the fluid Input force applied on the small piston produces pressure Large output force is produced at the large piston Area of piston = 2 cm2 Area of piston = 100 cm2 Figure 8.2 Piston Water Flask with fine pores Beaker 8.1.1 223 Chapter 8 Force and Pressure 8.1.1
Application of Pascal’s Principle in Daily Life The hydraulic system is used to carry out heavy work using a small force. Three examples where Pascal’s principle is applied in daily life are the hydraulic jack, hydraulic brake and dental chair. Hydraulic Jack System Hydraulic jack is usually used to lift heavy loads such as cars in workshops. Try operating a hydraulic jack. Figure 8.5 shows the structure of a hydraulic jack system. Lever Air hole Small piston Release valve Valve Liquid Large piston Load Valve Liquid reservoir Figure 8.5 Hydraulic jack system In the hydraulic jack system, the lever is moved downwards and upwards repeatedly to push the loaded large piston upwards with the release valve closed. When the release valve is opened, the loaded large piston will drop back to its original position as shown in Figures 8.6, 8.7 and 8.8. According to Pascal’s principle, the pressure exerted by the small piston is the same as the pressure produced at the large piston. Pressure at small piston = Pressure at large piston Input force Area of small piston = Output force Area of large piston 10 N 2 cm2 = Output force 100 cm2 Output force = 10 N × 100 cm2 2 cm2 = 500 N Photograph 8.2 Hydraulic jack Video Operation of hydraulic jack http://buku-teks. com/sc5225a 224 8.1.1 8.1.2
Operation of hydraulic jack system: (a) Increasing the height of a loaded large piston Pivot The lever is moved downwards with the release valve closed, valve A closes and valve B opens (The lever is moved downwards and upwards a few times to lift the load to a desired height) Valve B opens Lever is moved downwards Small piston exerts pressure on the liquid Valve A closes Air hole Liquid reservoir Release valve is closed Liquid transmits its pressure to the loaded large piston and pushes it upwards Large piston rises Load Figure 8.6 Large piston is raised (b) Maintaining the height or position of the large piston The lever is moved upwards with the release valve closed, valve A opens and valve B closes Load ➊ Lever is moved upwards Air hole Release valve is closed ➌ A constant liquid pressure is exerted on the large piston to maintain its position ➍ Position of large piston is maintained ➋ Liquid from reservoir flows below the small piston through the open valve A Valve B closes Valve A opens Liquid reservoir Figure 8.7 Position of large piston is maintained (c) Lowering the large piston back to its original position Figure 8.8 Large piston returns to its original position The release valve is opened, valve A opens and valve B closes Air hole ➊ Release valve is opened Large piston goes down to its original position ➋ Loaded large piston exerts pressure on the liquid beneath it ➌ The liquid flows back into the liquid reservoir through the release valve Valve A opens Valve B closes Liquid reservoir Scan Page 225 Chapter 8 Force and Pressure 8.1.2
The Hydraulic Brake System The hydraulic brake system is commonly used to slow down or stop wheeled vehicles such as moving cars. The operation of a hydraulic brake system is shown in Figure 8.9. Figure 8.9 The hydraulic brake system and its operation Dental Chair The operation of the dental chair is related to the hydraulic system. Observe the dental chair in Photograph 8.3. Then, study and understand the application of Pascal’s principle in the dental chair as shown in the following video or other sources of information. Video Is hydraulic system used in a dental chair? http://buku-teks.com/sc5226b Application of Pascal’s principle in a dental chair http://buku-teks.com/sc5226c Scan Page raulic s video Photograph 8.3 Dental chair Brake pedal Main piston Pivot Brake shoe Brake lining Brake drum Spring Metal pipe Brake cylinder Brake cylinder Pivot Steel plate mounted to front wheel Reservoir of brake oil Master cylinder Brake pad Disc brake Drum brake ➋ ➌ ➍ ➊ ➋ ➌ ➍ ➊ The brake pedal is pressed to push in the master cylinder piston to exert pressure on the brake oil. ➋ This pressure is transmitted uniformly by the brake oil through the metal pipes to the brake cylinders of the front and back wheels. ➌ This pressure pushes the piston in the brake cylinder which presses the brake pad onto the steel plate in the disc brake. ➍ The frictional force between the brake pad and the steel plate slows down or stops the rotation of the front wheels. ➌ This pressure pushes the piston in the brake cylinder which presses the brake shoe onto the brake lining on the drum brake. ➍ The frictional force between the brake lining and the brake drum slows down or stops the rotation of the back wheels. Disc brake at front wheel Drum brake at back wheel 226 8.1.2
h P1 P2 P3 Figure 8.10 Fluid pressure is the same in a fluid that is not flowing P1 P2 P3 Figure 8.11 The Venturi effect and Bernoulli’s principle Relationship between Fluid Velocity and Pressure Study and understand the relationship between fluid velocity and pressure (Figures 8.10 and 8.11). Figure 8.10 shows that the fluid pressure at P1, P2 and P3 is the same because the fluid is not flowing. A Venturi tube is a non-uniform tube with a narrower centre (Figure 8.11). In Figure 8.11, when the fluid starts to flow, the velocity of the fluid at P2 is higher than the velocity of the fluid at P1 and P3. The narrower the part of the Venturi tube, the lower the pressure in the fluid. This is known as the Venturi effect. When the fluid flows through the narrow part, its velocity increases and the pressure in that region decreases. This is known as Bernoulli’s principle. Video Venturi effect and Bernoulli’s principle http://buku-teks. com/sc5227 227 Chapter 8 Force and Pressure 8.1.3
Activity 8.2 To explain Bernoulli’s principle by using a Venturi tube Materials Tap water Apparatus Venturi tube, rubber tube and clip Instructions 1. Carry out this activity in groups. 2. Prepare the apparatus set-up as shown in Figure 8.12. 3. Close the clip. Turn on the tap and allow tubes X, Y and Z to be filled with water. 4. Observe and compare the height of the water level in tubes X, Y and Z. 5. Sketch your observations in figure (a). 6. Open the clip and the tap so that water flows into the sink continuously through the glass tube. 7. Repeat step 4. Sketch your observations in figure (b). Observations XY Z PQ R XY Z PQ R (a) (b) Questions 1. State the relationship between fluid velocity and pressure based on your observations of figures (a) and (b). 2. Name the effect of the change in pressure of the fluid which flows through the narrower part of the Venturi tube. 3. What is the principle shown in the observation in figure (b)? XY Z PQ R To the sink From the tap Clip Figure 8.12 Application of Bernoulli’s Principle in Daily Life Bernoulli’s principle states that a fluid moving at a higher velocity produces a lower pressure in that region. 21 Century Skills st • TPS • Inquiry-based activity 228 8.1.3 8.1.4
Aerofoil-shaped wings of an aeroplane Bunsen burner Helicopter Drone Safety lines near railway tracks at a railway station Figure 8.13 Bernoulli’s principle in daily life High velocity airflow, low air pressure Low velocity airflow, high air pressure Lift Lift High velocity airflow, low air pressure Low velocity airflow, high air pressure Force Safety lines near railway tracks High velocity airflow, low air pressure Low velocity airflow, high air pressure Lift Lift In the space between a moving train and a person standing near the safety lines, the velocity of the airflow is high and the air pressure is low. As such, there is a strong possibility for a person who stands beyond the safety lines to be pushed by force towards the moving train. Thus, avoid standing beyond the safety lines. Lift Low velocity airflow, high air pressure High velocity airflow, low air pressure Angle of attack Flow of gas and air mixture Gas Air with low velocity but high pressure will be sucked in High velocity gas, with low pressure The resulting lift on the wing of an aeroplane comes from: • aerofoil shape • angle of attack 229 Chapter 8 Force and Pressure 8.1.4
Activity 8.3 Activity 8.4 21 Century Skills st • TPS, ICS, STEM • Project-based activity To study the application of Bernoulli’s principle in daily life Instructions 1. Carry out this activity in groups. 2. Gather information from the Internet, print media and other electronic media on the application of Bernoulli’s principle in various sports such as sailing and windsurfing. 3. Discuss the information gathered. 4. Present the outcome of your group discussion in the form of a report. To design a tool using the principle of pressure in fluids Instructions 1. Carry out this activity in groups. 2. Design a tool such as a crane to lift heavy loads by using the hydraulic system. 3. Present the design of your tool. Discuss how the hydraulic system functions in the design of your tool. 8.1.4 8.1.5 Figure 8.14 An example of a tool design Formative Practice 8.1 1. State Pascal’s principle. 2. State the basic principle of the hydraulic system. 3. Give three examples of the application of Pascal’s principle in daily life. 4. State Bernoulli’s principle. 21 Century Skills st • ICS, ISS, TPS 230
Summary Summary Su Pressure in Fluids Pascal’s principle Bernoulli’s principle The transmission of pressure exerted on a fluid (liquid or gas) in an enclosed system is uniform throughout the fluid and in all directions A fluid which moves at a higher velocity produces a lower pressure in that region • Hydraulic jack • Hydraulic brake • Dental chair • Aerofoil-shaped wings of aeroplanes • Helicopters • Drones • Bunsen burners • Safety lines near tracks at railway stations 231 Chapter 8 Force and Pressure
Enrichment Practice Source of reference: Video on building a model of a dental chair http://buku-teks.com/sc5232b Self-Reflection Self-Reflection Summative Practice 8 Summative Practice 8 Quiz http://bukuteks.com/ sc5232a Figure 1 P0 P0 P1 P1 After studying this chapter, you are able to: 8.1 Pressure in Fluids Explain the concept of pressure in fluids in an enclosed system. Communicate about the application of Pascal’s principle in daily life. Explain the relationship between fluid velocity and pressure. Communicate about the application of Bernoulli’s principle in daily life. Design a tool using the principle of pressure in fluids. Answer the following questions: 1. Figure 1 shows two vehicles moving with the same velocity and producing two different pressures, P0 and P1. (a) Which pressure is lower? (b) Explain your answer in question 1(a). (c) Why is the situation of the two vehicles shown in Figure 1 dangerous? 2. A dental chair as shown in Figure 2 is an application of Pascal’s principle which plays an important role in helping dentists during the dental treatment of their patients. Dental chairs must be easily adjustable for the comfort of both patients and dentists. • Build a creative model of a dental chair by applying Pascal’s principle. • Describe the creative features of your model. • Discuss in your group on how the model can be modified into an automated massage chair. • Present your ideas to your class. Figure 2 232
What is the method used to send reusable launch vehicles into the orbit of the International Space Station (ISS)? Is it by direct transfer or through Hohmann transfer orbit? Earth and Space Exploration 4 HEME 233
SPACE TECHNOLOGY t4BUFMMJUF t(MPCBM1PTJUJPOJOH4ZTUFN (14 9 CHAPTER What are the types of orbits of Malaysian satellites which orbit Earth? Dato’ Dr. Sheikh Muszaphar Shukor Al Masrie bin Sheikh Mustapha is the first Malaysian astronaut to carry out scientific research at the International Space Station (ISS). How many days was he at the ISS? What is the final type of orbit taken by launch vehicles which carry astronauts, supplies and satellite equipment to reach the ISS? Let’s study L 234
Science Bulletin Science Bulletin r 5ZQFPGTBUFMMJUFPSCJU r -PX&BSUI0SCJU -&0 r .JEEMF&BSUI0SCJU .&0 r )JHI&BSUI0SCJU )&0 r (FPTZODISPOPVT0SCJU (40 r (FPTUBUJPOBSZ0SCJU (&0 r "QPHFF r 1FSJHFF r 0SCJUBMIFJHIU r 4BUFMMJUFTQFFE r )PINBOOUSBOTGFSPSCJU r &YQFOEBCMFMBVODIWFIJDMF &-7 r 3FVTBCMFMBVODIWFIJDMF 3-7 r *OUFSOBUJPOBM4QBDF4UBUJPO *44 r ;FSPHSBWJUZ r 4QBDFKVOL r (MPCBM1PTJUJPOJOH4ZTUFN (14 r /BWJHBUJPO r (14DPPSEJOBUFT r %.4GPSNBU r %%GPSNBU r (PPHMF.BQT r 8B[F Malaysia is among the first Asian countries to launch a 5G demonstration project Is 5G network currently used in telecommunications in Malaysia? 5G network, together with Global Satellite Network technologies, has clearly and widely benefited all parties all over the world. The Global Satellite Network enables the worldwide transfer of information from one country to another while 5G network is able to decipher the type of data required by local users. 5G network is also able to switch to lower level power when not in use and switch back to higher level power for purposes such as high-definition video streaming. Advancements in telecommunication technology widens the use of satellites in daily life. Name the satellite owned by Malaysia which can be used in the demonstration of 5G in this region. Source: http://buku-teks.com/sc5235 (Medium: bahasa Melayu) Keywords 235
LEO GEO GSO HEO MEO Geosynchronous Orbit (GSO) Orbital height of 35 786 km and orbital plane at an inclined angle to the equatorial plane Low Earth Orbit (LEO) Orbital height of 180 – 2 000 km High Earth Orbit (HEO) Orbital height equal to or exceeding 35 780 km Medium Earth Orbit (MEO) Orbital height of 2 000 – 35 780 km Geostationary Orbit (GEO) Orbital height of 35 786 km and the equatorial plane as its orbital plane Activity 9.1 Figure 9.1 Types of satellite orbits 9.1 Satellite A satellite is an object which orbits planets or stars. For example, the Moon is a natural satellite which orbits Earth. Besides natural satellites, there are many man-made satellites which orbit Earth. Types of Satellite Orbits The orbits of satellites which circle Earth are grouped into five types according to orbital height (altitude) (Figure 9.1). To gather information and explain the types of satellite orbits Instructions 1. Carry out this activity in groups. 2. Gather information from the Internet, print media and other electronic media about the types of satellite orbits, namely LEO, MEO, HEO, GSO and GEO. Examples of reference websites are as follows: Geosynchronous Orbit (GSO) Catalogue of types of and Geostationary Orbit (GEO) satellite orbits http://buku-teks.com/sc5236a http://buku-teks.com/sc5236b 3. Discuss the information that you gathered. 4. Present the outcome of your group discussion to the class. • ICS • Discussion 21 Century Skills st 236 9.1.1
Orbital Shapes There are two orbital shapes, perfectly circular and elliptical (Figure 9.2). GEO is an example of a perfectly circular orbit while MEO and HEO are examples of elliptical orbits. LEO and GSO are perfectly circular or elliptical. Apogee and Perigee of a Satellite in an Elliptical Orbit For satellites which make elliptical orbits, there are two specific positions in the orbits, which are apogee and perigee (Figure 9.3). Perigee Apogee Earth Figure 9.3 Apogee and perigee of a satellite in an elliptical orbit The apogee of a satellite in an elliptical orbit is the position of the satellite which is furthest from the planets or stars encircled by the satellite. How about the perigee of a satellite in an elliptical orbit? Relationship between Orbital Height and Satellite Velocity The types of satellite orbits, orbital heights and satellite speeds are shown in Figure 9.4. HEO Altitude: 35 780 km Speed: 11 100 km/h Altitude: 20 200 km Speed: 13 900 km/h Altitude: 705 km Speed: 27 500 km/h MEO LEO Earth Figure 9.4 Examples of types of satellites, orbital heights and satellite speeds The higher the orbital height of a satellite, the lower the satellite speed for it to remain in orbit. This is because the gravitational force on a satellite decreases when the orbital height of the satellite increases. Figure 9.2 Orbital shapes Perfectly circular Elliptical 237 Chapter 9 Space Technology 9.1.1 9.1.2 9.1.3
Activity 9.2 Activity 9.3 To draw a conclusion on the relationship between orbital height and satellite speed Instructions 1. Carry out this activity in groups. 2. Gather information from the Internet, print media and other electronic media about the types or systems of satellites, orbital heights and satellite speeds. 3. Tabulate the information and data gathered on orbital heights and satellite speeds. 4. Analyse the data gathered and draw a conclusion on the relationship between a satellite’s orbital height and its speed. 5. Present your group’s conclusion to the class. 21 Century Skills st • TPS, ICS • Inquiry-based activity What will happen to a satellite moving in a fixed orbit if its speed reduces too much? How about if its speed increases too much? Let us carry out Activity 9.2 to identify the relationship between orbital height and satellite speed. To explain how a satellite is placed into orbit Instructions 1. Carry out this activity in groups. 2. Gather information from watching the following video clip to explain how satellites are placed into orbit directly or through Hohmann transfer orbit. Watch the following video clip: http://buku-teks.com/sc5238b Start time 5:00/10:05 End time 9:14/10:05 3. Discuss your observations after watching the video. 4. Present the way satellites are placed into orbit as observed from the video to the class. Click@Web Launch and placement of satellite into orbit http://buku-teks. com/sc5238c 21 Century Skills st • ICS • Inquiry-based activity Launch and Placement of Satellite into Orbit Let us carry out Activity 9.3 to understand how a satellite is launched and placed into orbit directly or through Hohmann transfer orbit. Satellite Type of satellite orbit Orbital height (km) Satellite speed GEO MEO ISS LEO Example: Visit the following website to collect information about the height or altitude of satellite orbits for satellite’s GPS purposes. http://buku-teks.com/sc5238a Thinking Skills 238 9.1.3 9.1.4
Activity 9.4 21 Century Skills st • TPS, ICS • Inquiry-based activity Methods of Sending Launch Vehicles into Orbit Launch vehicles, which are made up of one or more rockets, are used to send satellites or spacecrafts into outer space. Figure 9.5 shows two ways to place satellites into orbits using launch vehicles. To differentiate ELV from RLV Instructions 1. Carry out this activity in groups. 2. Gather information from the Internet, print media and other electronic media about the differences between expendable launch vehicle (ELV) and reusable launch vehicle (RLV). 3. Present the differences between ELV and RLV using a multimedia presentation to the class. Launch vehicles are divided into two types: (a) expendable launch vehicle (ELV) (b) reusable launch vehicle (RLV) ELV Photograph 9.1 Launching of ELV and RLV by NASA RLV Let us carry out Activity 9.4 to look for information about the differences between ELV and RLV. Earth Rocket trajectory Figure 9.5 Ways to send launch vehicles into orbit (a) Directly into orbit (b) Hohmann transfer orbit Burning at apogee (Large Orbit) Burning at perigee Hohmann transfer (Small orbit) orbit Earth R' ① ② ③ R Scan Page 239 Chapter 9 Space Technology 9.1.4