§ Electrons are the negative charge carrier whiles holes are positive charge carriers. § Pure semiconductors act as insulators at low temperature because there are no free electrons available to act as charge carriers. § However, the number of free electrons increases as the temperature of the semiconductor rises. The heat energy supplied is converted to the kinetic energy of the electrons. As a result, more electrons are knocked free, producing more charge carriers. Therefore, semiconductors act as conductors at high temperatures. Doping § Doping is a process of adding a small amount of impurities into the crystalline lattice of semiconductors to increase their conductivity. § Atoms of the impurities added should have almost the same size as the atoms of the semiconductors. § By adding different kinds of impurities, two types of semiconductors can be obtained; the p-type semiconductor and the n-type semiconductors. TYPES OF SEMICONDUCTOR ASPECT P-TYPE SEMICONDUCTOR N-TYPE SEMICONDUCTOR Diagram Doping substance Boron, indium, gallium, aluminium Antimony, phosphorus, arsenic Type/Valency of atom Acceptor atom / trivalent Donor atom / pentavalent Majority charge carriers Hole Electron Minority charge carriers Electron Hole Current flow Semiconductor Diode § A semiconductor diode is an electric component which allows electric current to flow in one direction only. 97 Physics CHAPTER 5 ELECTRONICS
§ A semiconductor diode consists of an anode and a cathode. It allows current to flow in one direction from the anode to cathode. § A semiconductor diode is formed by joining a p-type semiconductor and a n-type semiconductor to form a p-n junction. § When a piece of p-type semiconductor and a piece of n-type semiconductor are joined together, some free electrons from the n-type semiconductor move across the junction into the p-type semiconductor and fill in the holes. These electrons in the p-type semiconductor prevent other electrons from the n-type semiconductor from moving across the junction. The region with fewer charge carriers, both electrons and holes, near the junction is known as the depletion layer. § The potential difference across the depletion layer is known as the junction voltage. § In order for electric current to flow through the diode, the voltage applied across the diode must exceed the junction voltage. § A diode can be forward biased or reverse biased depending on the polarity of the potential difference applied across the ends of the diode. TYPES OF DIODE CONNECTION FORWARD BIASED CIRCUIT REVERSE BIASED CIRCUIT When a diode is forward biased, the holes will move towards the n-type semiconductor while the electrons will move towards the p-type semiconductor. When a diode is reverse biased, the holes and the electrons will both move away from the depletion layer in opposite directions. Depletion layer becomes and thinner and finally disappeared Depletion layer becomes thicker Junction voltage, V across the depletion layer decreases and the resistance of the diode becomes very small Junction voltage, V across the depletion layer increases until it reaches the potential difference of the battery. The resistance of the diode becomes very high. The current passes through the diode and the bulb lights up The current stops flowing, and the bulb does not light up 98 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
The Use of Semiconductor Diode and Capacitor in the Rectification of Alternating Current § Rectification is a process of converting an alternating current to a direct current. § There are two types of rectification which are: a) Half-wave rectification b) Full-wave rectification Half-Wave Rectification § A complete cycle of alternating current consists of two-half cycles which are: a) Positive-half cycle b) Negative-half cycle § During the positive half cycle, the semiconductor diode is forward biased and allows current to flow through it. § During the negative half cycle, the semiconductor diode is reverse biased and there is no current flow. § This half-cycle rectification process is called half-wave rectification. Full-Wave Rectification § A bridge rectifier is an arrangement that allows a complete cycle of current to flow in the same direction through the load, R. Positive half cycle Negative half cycle Diodes D1 and D2 are forward biased while D3 and D4 are reversed biased Diodes D3 and D4 are forward biased while D1 and D2 are reversed biased Capacitors in Smoothing Direct Current § Half-wave and full-wave rectifications produce a direct current which is not smooth. § A capacitor is used to smooth the current in a rectification circuit. Physics Bytes A capacitor is a device which can store electrical charges. 99 PhysicsCHAPTER 5 ELECTRONICS
SMOOTHING PROCESS HALF-WAVE RECTIFICATION OUTPUT FULL-WAVE RECTIFICATION OUTPUT § Capacitor is connected in parallel to the load, R. When the power supply is turned on, the output current becomes smooth. § When the potential difference increases, the capacitor will be charged and energy is stored in the capacitor. § When the potential difference decreases, the capacitor will discharge so that the output current does not fall to zero. The energy stored in the capacitor will maintain the potential difference across the resistor, R. § The smoothed output waveform shows that the capacitor is functioning as a smoother. EXAM WATCH Ammeter in diagram below shows no reading when the circuit is connected. A Increase the number of diodes B Reverse the terminal of dry cells C Increase the number of dry cells D Swap the position of ammeter and voltmeter Diagram shows connection of a diode in a simple circuit. Which of the following statement is correct when the switch is on? A The bulb is not light up B Connection of diode is reverse biased C Depletion region will getting larger D Current flow in the circuit SBP 2023 Question 37 Melaka 2023 Question 35 COMPONENTS OF TRANSISTOR TERMINAL FUNCTION Emitter, E Supply the charge carrier to the collector Base, B A thin layer in the centre of the transistor to control the flow of the charge carrier from the emitter to the collector. Collector, C Receive charge carriers from the emitter 100 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
TYPES OF TRANSISTOR NPN TRANSISTOR PNP TRANSISTOR The arrow in the symbol shows the direction of current from B and E. The arrow in the symbol shows the direction of current from E and B. 1 Transistors are often found in digital circuits such as computers. 2 A transistor circuit consists of two main parts, base circuit and collector circuit. npn transistor circuit pnp transistor circuit 3 When the switch is opened, the bulb L1 does not light up due to incomplete base circuit and base current, IB is zero. Bulb, L2 does not light even though the collector circuit is complete because the transistor is not turned on and the collector current, IC is zero. 4 When the switch is closed, the bulb, L1 is dimmed due to the resistor, RB with high resistance and base current, IB is very small. Bulb, L2 lights up brightly due to collector current, IC is large compared to base current, IB. 5 A small base current produces a voltage, VBE. When VBE reaches a minimum value, the collector circuit will be turned on. 6 Base current, IB can control th flow of collector current, IC. This condition allows the transistor to act as a switch. 7 Resistance, RB is large to limit the base current, IB so that the transistor does not become hot and flammable. A Transistor Functions as a Current Amplifier 1 Transistor acts as a current amplifier as the increase of small base current, IB results a large change in the collector current, IC. 2 In a transistor circuit, the power supply or battery will supply a fixed potential difference. The transistor requires a potential difference, VBE which is more than the minimum voltage for it to function. 3 To acquire a small potential difference, a potential divider circuit can be used. 4 In the potential divider method, two resistors with resistances, R1 and R2 should be connected in series with a power supply Vin. 5 As the current is flowing through both the resistors, the relationship between the voltage and the resistance is shown by the following equation. *+, =$ & + $ -. Amplification Factor, =/ 0 101 Physics CHAPTER 5 ELECTRONICS
THE USE OF A TRANSISTOR AS AN AUTOMATIC SWITCH LIGHT-CONTROLLED SWITCH HEAT-CONTROLLED SWITCH Light-dependent resistor (LDR) is a type of resistor which its resistance changes with the intensity of light. Light intensity increases, LDR resistance value decreases Thermistor is a resistor whose the resistance changes with its surrounding temperature. Room temperature condition (low temperature), resistance of thermistor increases. In the dark § Resistance of LDR increases. § Voltage across LDR increases. § Voltage across decreases. § Base current, ! flows and turns on the transistor. § Collector current, " flows and bulb lights up. In a bright environment § Resistance of LDR decreases. § Voltage across LDR decreases. § Volage across increases. § Base current, ! does not flow and transistor cannot be switched on. § Collector current, " does not flows and bulb does not light up. § When temperature increases, resistance of thermistor decreases. § Voltage across thermistor decreases. § Voltage across increases. § Base current, ! flows and transistor is turned on. § High value of collector current, " flows and the alarm rings. Use as automated light switch. (light up in the dark, turn off in bright condition) Use in fire alarm system. ✏ CHECKPOINT Diagram shows a light-controlled circuit for a lamp. Resistor R has a resistance of 10 kΩ. The minimum base voltage must be at least 0.7 V to turn on the 6 V, 0.3 W bulb. What is the resistance of the LDR when the bulb lights up? 102 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
EXAM WATCH Diagram shows a circuit with a transistor that acts as an automatic switch. Explain what happen to the light emitting diode (LED) when resistor X is in the dark. [4] Diagram below shows four electronic circuits W, X, Y and Z with different specifications. You are required to determine the most suitable circuit to light up three street lights 95 V, 65 W automatically with normal brightness when it is dark. W Y X Z Study the specifications of all the four circuits based on the following aspects: § The position of the light dependent resistor (LDR) § The connection of the batteries § The arrangement of the street lights circuit. § The use of a relay switch in the circuit. Determine the most suitable circuit diagram to be chosen and give one reason for your choice. [10] Aspect Reason MPSM 2021 Question 10 103 Physics CHAPTER 5 ELECTRONICS
Diagram below shows an incomplete fire alarm system circuit. Electronic component set AB CD EF GH S Dry cell X LED LDR Resistor T Dry cell Y Electric bell Thermistor Resistor U Dry cell X Electric bell LDR Rheostat V Dry cell Y LED Thermistor Rheostat Study and explain the suitability of electronic components in the table above. Determine the electric component set that is most suitable for ensuring the fire alarm system functions and rings when the temperature increases when there is fire. Provide reasons for your choice. [10] Aspect Reason SBP 2023 Question 10 104 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
"UNLOCKING THE ATOMIC SECRETS THAT FUEL BOTH THE STARS ABOVE AND THE TECHNOLOGIES OF TOMORROW." NUCLEAR PHYSICS 6S P M P H Y S I C S
CHARACTERISTICS OF RADIOACTIVE EMISSIONS CHARACTERISTICS ALPHA PARTICLE, BETA PARTICLE, GAMMA RAY, Nature Helium nucleus Fast moving electrons Neutral electromagnetic wave with high frequency Symbol / Nuclide notation !He " #$% − Charge +2 −1 0 Mass Large Very small No mass Ionising Power Strong Moderate Low Penetrating power Low Moderate High In an electric field Deflected towards negative plate Deflected towards positive plate No deflection In a magnetic field Slightly deflected Highly deflected No deflection 106 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
Radioactive Decay 1 Radioactive decay is a process in which an unstable nucleus becomes more stable by emitting radioactive radiation. 2 Radioactive decay process occurs randomly and spontaneously because it is not affected by factors such as temperature, pressure and so on. Alpha Decay 1 Alpha particle is a helium nucleus which consists of two protons and two neutrons. 2 During alpha decay, an unstable nucleus releases an alpha particle to become a more stable nucleus of a new element. !X" → !#$Y "#% + $He % Example &$U $'( → &)Y $'% + $He % Beta Decay 1 Beta particle is a fast-moving electron. 2 During beta decay, a neutron in an unstable nucleus decomposes into one proton and one electron. !X" → !*+Y" + #+) 3 The resulting proton remains in the nucleus while the electron is emitted with high kinetic energy as -particle. Example &)Th $'% → &+Pa $'% + #+) Gamma Decay 1 Gamma rays are high-frequency electromagnetic wave. 2 During gamma decay, an unstable nucleus releases its excess energy to become more stable. X∗ ! " → !X" + Example Co∗ $- .) → $-Co .) + 107 Physics CHAPTER 6 NUCLEAR PHYSICS
Half-life, 1 The half-life, # $ is the time taken for a sample of radioactive nuclei to decay to half of its initial number. 2 After one half-life, the number of nuclei that are not decayed will be half of its initial value. 3 When an unstable radioactive nucleus decays, the new nucleus that is formed may also be unstable. 4 The new nucleus will experience a series of continuous decay until a stable nucleus is formed. 5 Diagram below shows a complete decay series from uranium-238 to lead-206. To Determine the Half-life of a Radioactive Substance from its Decay Curve 1 Different radioactive substances decay at different rate. 2 A decay rate can be determined from a decay curve. 3 The activity of a radioactive sample is directly proportional to the number of radioactive nuclei present in the sample at that time. 4 The activity of a radioactive sample is the number of decays per second, which is the number of radioactive particles emitted per second. 5 The concept of half-life can be expressed as follow: Number of radioactive nuclei that has not decayed, = 6 + $ 7 / ) 6 The shorter the half-life of a radioactive sample, the higher the rate off decay. ✏ CHECKPOINT 1 A sample of radioactive material stored in the laboratory has an initial activity of 1680 s-1. If its half-life is 5 minutes, how much is its activity after 30 minutes? 108 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
2 A radioactive material stored in the laboratory has a half-life of 15 days. Calculate the number of days taken for the activity of a sample of radioactive material to reduce to 12.5 % of its initial activity. 3 Diagram below shows the decay rate of sodium-24. a) What is the half-life of sodium-24? b) Find the undecayed activity left after fourth half-life is completed. EXAM WATCH The half-life of Gallium-65 is 5 minutes. How long does it take for 90% if a Galium-65 atom to decay? A Less than 15 minutes B Equal to 15 minutes C More than 15 minutes The initial mass of a radioactive element is 40 g and its half-life is 10 days. Calculate the mass of radioactive elements remaining after 40 days. A 2.5 g B 5.0 g C 10.0 g D 20.0 g Kelantan 2023 Question 37 SBP 2022 Question 38 109 Physics CHAPTER 6 NUCLEAR PHYSICS
Diagram shows a decay curve of Uranium-238 into a stable lead-206. Based on the diagram, explain the Uranium decay process. [4] Several rocks were discovered at a volcanic site which contains Argon-40 which decays and forms Potassium-40. Table shows the characteristics of four rocks P, Q, R and S. Rocks Quantity of Argon Quantity of Potassium Ratio of Potassium to Argon Radioactive activity P High Low Low High Q Low High High Low R Low High Low Low S High Low High High Based on the information given, you are required to determine the most ancient rock. Give reasons for your choice. [10] Aspect Reason MRSM 2022 Question 9 110 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
1 Nuclear energy(atomic energy) is the energy needed to tie the individual protons and neutrons in a nucleus. 2 This binding energy is released during nuclear reactions such as radioactive decay, nuclear fission and nuclear fusion. 3 Total mass of the products in a nuclear reaction is less than the mass of the parent nucleus. The mass difference (mass defect, ∆) is released as nuclear energy. Nuclear Fission Nuclear fission is a nuclear reaction when a heavy nucleus splits into two or more lighter and stable nuclei while releasing a large amount of energy. Nuclear Fusion Nuclear fusion is a nuclear reaction in which small and light nuclei fuse under extremely high temperature and pressure to form a heavier nucleus while releasing a large amount of energy. The Relationship between Energy Released during Nuclear Reaction and Mass Defect 1 Mass of an atom is measured by using atomic mass unit (a.m.u) or u. 2 It is a relative comparison between a mass of an atom and mass of a carbon-12 atom. 3 The mass of carbon-12 atom is 12 u. 4 1 u is defined as a mass equal to + +$ mass of a carbon-12 atom. (1 u = 1.66 × 10-27 kg) = $ = total energy released = mass defect (kg) = speed of light in vacuum 5 Nuclear energy can be expressed in the unit of megaelectronvolts, MeV. (1 MeV = 1.60 × 10-13 J) 111 PhysicsCHAPTER 6 NUCLEAR PHYSICS
✏ CHECKPOINT 1 The following equation shows radium-226 decaying into radon-222 by emitting alpha particle. ((Ra $$. → (.Rn $$$ + $He % Given that the mass of ((Ra $$. is 226.0254 u, (.Rn $$$ is 222.0178 u and $He % is 4.0026 u, calculate the nuclear energy released. [1 u = 1.66 × 10-27 kg and speed of light in vacuum, c = 3.00 × 108 m s-1] 2 The source of energy to the Earth is the Sun. The Sun energy is produced by nuclear fusion in the core of the Sun as the following. +H$ + +H' → $He % + )n+ + energy Find the nuclear energy released in joules. [mass +H$ = 2.014102 u, mass +H' = 3.016049 u, mass $He % = 4.002603 u, mass )n+ = 1.008665 u, 1 u = 1.66 × 10-27 kg and speed of light in vacuum, c = 3.00 × 108 m s-1] 3 The following shows the equation of some nuclear reaction. &$U $'0 + )n+ → 00Cs +%+ + '-Rb &' + 2)n+ + energy The mass defect is 0.19585 u. What is the energy released by the reaction? 112 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
EXAM WATCH A nuclear reaction is represented by the following equation. +H$ + +H$ → +H' + +H+ What is the mass defect produced in the above reaction? [+H+ = 1.007825 u, +H$ = 2.014102 u, +H' = 3.016049 u, 1 u = 1.66 × 10-27 kg] A 4.85 × 1027 kg B 2.61 × 1024 kg C 1.34× 10-26 kg D 7.19 × 10-30 kg Diagram below shows the mushroom cloud produced during the Trinity atomic bomb test which was invented by J Robert Oppenheimer. The total energy produced from this explosion is 100 × 1012 J. What is the total mass defect? A 1.11 × 10-3 kg B 3.33 × 10-3 kg C 1.11 × 105 kg D 3.33 × 105 kg SBP Model Paper Set 3 Question 37 SBP 2023 Question 38 Chain reaction EXAM WATCH Nuclear fission produce a chain reaction. Describe how the chain reaction happens in a nuclear fission of an atom of uranium. [4] SBP Model Paper Set 2 Question 10 Generation of Electrical Energy in a Nuclear Reactor Nuclear reactor is used to generate electricity. However, in Malaysia, the existing nuclear reactors are only for research purposes. 113 Physics CHAPTER 6 NUCLEAR PHYSICS
1 2 3 4 5 § Nuclear fission (uranium-235) § Chain reaction produce heat energy § Water is pumped into the reactor core to absorb heat energy § Boiling of water produces steam with high pressure § Channelled to the turbine § Turbine is rotated § Magnet/coil in the generator is also rotated. § Steam will condense into water § Electrical energy is generated EXAM WATCH Diagram shows a cross section of nuclear reactor model. The nuclear reactor is designed to generate electrical energy. Using the knowledge on nuclear energy, suggest a nuclear reactor design that has high efficiency to generate electrical energy. In your explanation, emphasize on the type and half-life of fuel, the material of the rod, the material of moderator and type of shield. [10] Fuel: Reason: State of fuel: Reason: Half-life: Reason: Control rod: Reason: Moderator: Reason: Type of shield: Reason: SBP Model Paper Set 2 Question 11 Control rod: § Boron / cadmium § Absorb excess neutrons Moderator: § Graphite / water § Slow down fast moving neutrons Uranium rods: § As fuel Thick concrete wall: § Prevent leakage of radioactive radiation Cooling agent: § Water § Absorb heat energy 114 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
"DELVING INTO THE MIND-BENDING REALMS WHERE PARTICLES DANCE IN UNCERTAINTY, UNVEILING THE MYSTERIES OF THE SMALLEST SCALES AND THE GRANDEST COSMIC TAPESTRIES." QUANTUM PHYSICS 7S P M P H Y S I C S
Electromagnet spectrum is a continuous spectrum that consists of seven types of waves with different frequencies and wavelength. Black Body Radiation 1 Any object with a temperature above absolute zero emits electromagnetic radiation at all wavelengths. 2 Objects with low temperature emit waves with low frequencies such as radio waves or microwaves. 3 Objects with high temperature emit waves with high frequencies such as visible light and ultraviolet radiation. 4 A black body is an idealised body that is able to absorb all electromagnetic radiation that falls on it. 5 A black body also emit thermal radiation / electromagnetic radiation (visible light, infrared radiation) depending on its temperature and is known as black body radiator. 6 The emitted radiation forms a continuous spectrum and is unaffected by the nature of the black body surface. 7 As the temperature of an object rises, the object (black body radiator) emits thermal radiation at all wavelength. BLACK BODY PERFECT EMITTER (RADIATOR) PERFECT ABSORBER The Sun is a near perfect blackbody emitter because it emits the whole electromagnetic spectrum at different radiation intensities in thermal radiation. A cavity with a small hole is a near-perfect blackbody absorber as most, if not all, electromagnetic waves that enter the cavity through the hole are absorbed or trapped in the cavity. Physics Bytes The energy of blackbody radiation is not shared evenly by all wavelengths. The intensity becomes nearly zero at the short wavelength, high frequency side. 116 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
EXAM WATCH Diagram shows rays of light enter the ear cavity. Explain how the ear cavity can act like a black body. [3] MRSM 2023 Question 4 Development of Quantum Theory from Classical Theory 1 In a hot object, electrons vibrate rapidly and randomly in any direction and produce light. 2 The hotter the object, the higher the energy of electron vibration. Thus, more light will be emitted. 3 As stated in classical theory, the electron that vibrates at the same frequency should have the same energy content. 4 The light energy produced able to reach unlimited high value due to the frequency of the electrons has no limit. 5 When the temperature of the black body increases, the intensity of radiation also increases and will not become zero. 6 However, the experimental results of black-body radiation are inconsistent with classical physics theory. 7 This failure of classical physics leads to the advent of quantum physics to explain the blackbody radiation curved based on the concept of discrete energy packet known as quantum of energy. 117 Physics CHAPTER 7 QUANTUM PHYSICS
Quantum of Energy 1 Quantum of energy is discrete energy packet and not a continuous energy. 2 The discrete energy packets depend on the frequency of the wave. 3 The concept of continuous energy can be explained by using visible light spectrum(continuous energy) and line spectrum (discrete energy) of hot mercury vapour. Dalton atomic theory § Atom is a particle that cannot be subdivided John Dalton § Conduct Young’s double slit experiment as showed light is a wave. § Unable to explain the radiation spectrum produced by black bodies. Thomas Young Classical Theory Quantum Theory § Describe light as stream of particles or corpuscles § Unsuccessful in explaining light refraction due to failure in comparing speed of light in glass and air Isaac Newtown § Introduced the idea of discrete energy quantum § The electromagnetic wave emitted by a black body is in the form of quantum of energy. § The energy in each quantum is directly proportional to the wave frequency. Max Planck § Concept of photon § Photon energy is directly proportional to the frequency of light waves. § Photoelectric effect Photon energy = ℎ Albert Einstein § Line spectrum of hydrogen atoms § Electrons in an atom orbit around its nucleus on certain shell only § Transition of electrons from a higher energy level to a lower energy level emits photons Neil Bohr § Discovered negatively charged particle (electrons) § Designed an experiment to study the behaviour of electrons J.J. Thomson Wave particle duality of light and all subatomic particles Louis de Broglie 118 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
TYPES OF SPECTRUM CONTINUOUS SPECTRUM (CONTINUOUS ENERGY) LINE SPECTRUM (DISCRETE ENERGY) § Produced through dispersion of white light by a prism that consists of seven visible colours § Continuous because there is no separation gap between each colour in the spectrum § Produced by an excited atom is a sereis of coloured lines with unique wavelengths and frequencies § Each element produces a spectrum with a series of its own distinctive lines § Line spectrum can be used to identify the prescence of an element 4 Based on Max Planck and Albert Einstein’s quantum theory, light energy exists in the form of an energy packet known as a photon. 5 Photons are light energies transferred in quantum energy. = ℎ = ℎ ✏ CHECKPOINT Calculate the photon energy for light with wavelengths 450 nm and 700 nm. Compare both photons. 6 Photon power, is the total energy transfer in one second. = ℎ = photon energy ℎ = Planck’s constant (6.63 × 10-34 J s) = frequency of light = speed of light (3.00 × 108 m s-1) = wavelength = number of photons emitted per second 119 PhysicsCHAPTER 7 QUANTUM PHYSICS
✏ CHECKPOINT 1 How many photons are emitted per second by ultraviolet light with wavelength, = 4.4 × 10-7 m, powered by 50 W? 2 A laser device emits light with a wavelength of 700 nm. If the number of photons emitted is 3.37 × 1018 per second, determine the output power of the laser. Wave-Particle Duality 1 Light has wave properties because it shows the phenomena of diffraction and interference. 2 Object has particle properties because it has momentum, kinetic energy and also collide with each other. 3 Louis de Broglie introduced a hypothesis state that all particles exhibit wave characteristics. 4 However, it is experimentally difficult to show the wave characteristics of particles with large masses. 5 Thus, Louis de Broglie predicted that the wave characteristics can be shown by light particles such as electron, proton and neutron. = ℎ = ℎ 6 Since the value of ℎ is too small, the particle with large mass will have too short of de Broglie wavelength to be detected. Thus, the wave characteristics cannot be observed. 7 The presence of wave properties of electrons was confirmed through the electron diffraction experiments. Diffraction pattern of electrons through a thin layer of graphite Diffraction pattern of a red laser light through an aperture = wavelength ℎ = Planck’s constant (6.63 × 10-34 J s) = momentum 120 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
8 The de Broglie wavelength of an electron beam is approximately 1000 – 10 000 times shorter than the wavelength of light. This characteristic is important for higher magnification of electron microscope. ✏ CHECKPOINT Given that the mass of an electron, ! is 9.11 × 10-31 kg, calculate the de Broglie wavelength of an electron beam with 30 eV kinetic energy. [1 eV = 1.60 × 10-19 J, Planck’s constant, ℎ = 6.63 × 10-34 J s] 1 Photoelectric effect occurs when a metal surface is illuminated by a beam of light at a certain frequency, the electrons can be emitted. 2 Diagram shows a photocell circuit to show the photoelectric effect. a) When a light sensitive metal surface (cathode) is illuminated with a certain light beam, electrons will be emitted from the metal surface. Those electrons are called photoelectrons. b) The emitted photoelectrons are attracted to the anode which has positive potential. c) The movement of the photoelectrons from the cathode to the anode produces a photocurrent inside the circuit. The milliammeter shows the value of this current. 121 Physics CHAPTER 7 QUANTUM PHYSICS
CHARACTERISTICS OF PHOTOELECTRIC EFFECT CHARACTERISTIC UNEXPLAINED USING CLASSICAL THEORY The minimum frequency of light required for a metal to emit electrons is known as threshold frequency, for that metal. For example, the threshold frequency, " for potassium is 5.46 × 1014 Hz. According to the classical theory, electrons are emitted from a metal surface when light waves strike on it. As light waves from a continuous spectrum of different frequencies, photoelectric effect can happen at all frequencies of light striking on a metal surface. The higher the frequency of light which strikes the surface of a metal, the higher the kinetic energy of the photoelectrons emitted from the metal surface. Light energy of all frequencies absorbed by photoelectrons emitted from the surface of a metal by photoelectric effect is converted into kinetic energy. The kinetic energy of photoelectrons dows not depend on the intensity of light. An increase in the light intensity does not produce photoelectrons of higher kinetic energy. As the kinetic energy of the photoelectrons depends on the energy of light waves striking the metal surface, the higher the intensity of light, the higher the kinetic energy of the photoelectrons emitted by the photoelectric effect. Photoelectrons are emitted instantaneously from a metal surface by photoelectric effect. Electrons emitted from a metal surface by thermionic emission take some time for the metal surface to get hot. Threshold frequency, is the minimum frequency required to produce photoelectric effect on a metal. EXAM WATCH Which of the following is correct about photoelectric effect? A Photoelectrons are emitted instantaneously B Photoelectrons are emitted at any light frequencies C The kinetic energy of a photoelectron depends on the intensity of light D Photoelectrons are emitted at light frequency that is less than threshold frequency A photon of electromagnetic wave has the same momentum with an electron which move at speed of 2.0 × 106 m s-1. What is the de Broglie wavelength of the photon? [Mass of electron = 9.11 × 10-31 kg] A 2.75 × 109 m B 6.86 × 10-4 m C 3.64 × 10-10 m D 3.33 × 10-10 m MRSM 2023 Question 39 Terengganu 2023 Question 40 122 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
1 Einstein’s Photoelectric Theory is a photoelectric theory that successfully explained all the characteristics of photoelectric effect in related experiments. 2 Through the idea of quantum energy by Max Planck, Einstein suggested that the energy is carried by light particles called photons. 3 The energy of each photon is directly proportional to the frequency, . 4 Each quantum of light is a discrete packet of energy. There are many energy packets in a beam of light that shines on the metal surface. 5 When a photon arrives at a metal surface, the photon energy will be fully absorbed by an electron in the metal and the extra energy will become the kinetic energy of the photoelectron. 6 Commonly the electrons on a metal surface will obtain maximum kinetic energy compared to the electrons inside the metal. photon energy = minimum energy to release a photoelectron + maximum kinetic energy of a photoelectron = + #$% Work Function and Threshold Frequency for Photoelectric Effect 1 Work function, is the minimum energy for a photoelectron to be emitted from a metal surface. 2 Photoelectrons will acquire kinetic energy when light frequency exceeds threshold frequency. 3 The higher the threshold frequency of a metal, the higher the work function. 4 Different metals have different threshold frequencies. 123 Physics CHAPTER 7 QUANTUM PHYSICS
✏ CHECKPOINT 1 Find the maximum kinetic energy of electron emitted form a clean caesium metal surface that is shone by a light frequency of 5.34 × 1014 Hz. [Work function of caesium, = 3.43 × 10-19 J and Planck’s constant, ℎ = 6.63 × 10-34 J s] 2 Find the maximum velocity of emitted photoelectron when a monochromatic light of = 450 nm is shone on a metal. The work function of the metal is 2.00 eV. [Given ℎ = 1.243 × 103 eV nm, 1 eV = 1.6 × 10-19 J, and mass of photoelectron, = 9.11 × 10-31 kg] 3 When a photocell is shone on with a red light (& = 750 nm) and then with a blue light (' = 460 nm), the maximum kinetic energy of the photoelectron emitted by the blue light is 2.5 times that of the red light. a) Find the work function of the photoelectric material in the photocell. b) Determine the threshold wavelength of the photoelectric material. [Planck’s constant, ℎ = 6.63 × 10-34 J s, speed of light in vacuum, = 3.00 × 108 m s-1] Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics 124 Physics
4 A metal surface has a work function of 3.0 eV and is illuminated with a light ray of 350 nm. a) Determine the maximum wavelength that causes the photoelectric emission. b) What is the maximum kinetic energy of the photoelectron. c) What is the speed of photoelectron? Generating Photoelectric Current in a Photocell Circuit 1 Photocell circuit consists of a glass vacuum tube. 2 The semi-cylindrical cathode is coated with a light-sensitive metal and connected to the negative potential. 3 The anode is a metal rod fixed at the axis of the semi-cylindrical cathode and connected to the positive potential. 4 The photoelectric current is produced in the circuit when the photocell is illuminated by light. PHOTOCELL TYPE OF METAL (CATHODE) CAESIUM LITHIUM Diagram Work function, = 2.14 eV = 2.50 eV Threshold frequency, " " = 5.16 × 1014 Hz " = 6.03 × 1014 Hz Maximum wavelength to produce photoelectric effect " = 579 nm " = 496 nm 5 As light intensity increases, the photoelectric current in the photocell circuit also increases. 125 Physics CHAPTER 7 QUANTUM PHYSICS
Photoelectric Effect Application 1 Solar cell § Applications of solar cell are energy efficient and environmentally friendly because during daylight, photoelectric effect of solar cells enables electrical energy to be stored in the battery. § The stored energy can be used at night. § The applications of solar cell are LED lamp along the road, solar power plant, and energy source International Space Station (ISS). 2 Light detector of automatic door § Light detectors at the automatic doors use infrared beam and photocells as switches. § When the light path is disturbed, photoelectric current in the photocell circuit will be disconnected and the door will remain open. 3 Image sensor § The image sensor is a main component in high resolution cameras. § This component is used to store and process the images and videos in electronic component such as smart phone camera and CCTV. § Information data of image and video are stored in digital form to ease the processing data. EXAM WATCH A light of wavelength 400 nm is incident on a metal surface to produce photoelectrons. If the threshold wavelength of the metal is 652 nm, what is the maximum kinetic energy of the photoelectrons? A 2.89 × 10-20 J B 4.00 × 10-20 J C 1.04 × 10-19 J D 1.92 × 10-19 J The maximum wavelength able to release electron from sodium surface is 650 nm. Determine the maximum kinetic energy of electron ejected from sodium surface if light of wavelength 436 nm is incident on its surface in vacuum. A 1.50 × 10-18 J B 1.50 × 10-19 J C 3.06 × 10-19 J D 4.56 × 10-19 J SBP 2023 Question 40 Melaka 2023 Question 40 The photocells applying the photoelectric effect have many practical applications in our daily life. You are required to investigate the features of photocells as shown in the table. Photocells Light source Light source intensity Type of photocell Work function S Red High Semiconductor Medium T White Low Vacuum tube High U Infrared Low Semiconductor Low V Ultraviolet High Vacuum tube Low Explain the suitability of each characteristic of photocells above which is to be used in an automatic door system of a shopping mall. Determine the most suitable photocell. Give reason for your choice. [10] Aspect Reason Yakin Model Paper Set 1 2022 Question 10 126 Physics Force and Mo+on II Pressure Electricity Electromagne+sm Electronics Nuclear Physics Quantum Physics
Form 4 Chapter 1 Measurement 1.1 Physical quantity A quantity that can be measured Base quantity A physical quantity that cannot be derived from other physical quantity Derived quantity Aquantitywhichcanbeobtainedby combinationofbasequantitiesby mean of multiplication, division or both Scalar quantity Physical quantities that have magnitude only Vector quantity Physical quantities that have both magnitude and direction Chapter 2 Force and Motion I 2.1 Linear motion Motion in a straight line Speed, Rate of change of distance Velocity, Rate of change of displacement Acceleration, Rate of change of velocity 2.3 Free fall motion A situation where the motion of object is acted upon by gravitational force only 2.4 Inertia Tendency of an object to remain at rest or to continue its uniform motion in a straight line at uniform velocity Newton’s First Law of Motion An object will remain at rest or move at uniform velocity unless acted upon by an external force 2.5 Momentum, A product of mass multiplies by velocity 2.6 Force, Push or pull Newton’s Second Law of Motion Rate of change of momentum is directly proportional to the force and acts in the direction of the applied force 2.7 Impulse, Change of momentum Impulsive Force, Rate of change of momentum in a collision or impact in a short period of time Newton’s Third Law of Motion For every action there is a reaction of equal magnitude but in the opposite direction 2.8 Weight, A gravitational force acting on an object Chapter 3 Gravitation 3.1 Newton’s Universal Law of Gravitation The gravitational force between two objects is directly proportional to the product of masses of both objects and inversely proportional to the square of the distance between them. Centripetal force A force acts on the body in a direction towards the centre of the circle and perpendicular to the linear velocity 3.2 Kepler’s First Law All planets move in elliptical orbits with the Sun at one focus (Law of Orbits) Kepler’s Second Law A line that connects a planet to the Sun sweeps out the equal areas in equal times (Law of Areas) Kepler’s Third Law The square of the orbital period of any planet is directly proportional to the cube of the radius of its orbit (Law ofPeriods) Orbital radius Average value of the distance between the planet and the Sun 3.3 Escape velocity, Minimum velocity needed by an object on the surface of the Earth to overcomethe gravitational force and escape to outer space Chapter 4 Heat 4.1 Temperature, Measure of the degree of hotness of an object Heat, The amount of thermal energy that can be transferred from one object to another Thermal equilibrium A condition where net heat transfer between two objects becomes zero 4.2 Heat capacity, Quantity of heat needed to raise temperature of the object by 1°C Specific heat capacity, Quantity of heat needed to raise the temperature of 1kg mass of the substance by 1°C 4.3 Latent heat Heat that is absorbed during melting and boiling without change in temperature Specific latent heat, The quantity of heat that is absorbed or released during a change of phase of 1kg of the substance without any change in its temperature Specific latent heat of fusion, ! The quantity of heat that is absorbed during melting or the quantity of heat released during freezing of 1kg of the substancewithout any change in temperature (solid-liquid |liquid-solid) Specific latent heat of vaporisation, " The quantity of heat that is absorbed during boiling or the quantity of heat released during condensation of 1kg of the substance without any change in temperature (liquid-gas |gas-liquid) 4.4 Boyle’s law Pressure is inversely proportional to volume for a fixedmass of gas at constant temperature Charles’ law Volume is directly proportional to absolute temperature for a fixed mass of gas at constant pressure Gay-Lussac’s law Pressure is directly proportional to absolute temperature of a fixed mass of gas at constant volume 127 PhysicsAPPENDIX DEFINITION LIST
Chapter 5 Waves 5.1 Oscillation, vibration Repetitive motions about an equilibrium position in a closed path Amplitude, Maximum displacement from its equilibrium position Transverse wave A wave which the vibration of particles in the medium is perpendicular to the direction of propagation of the wave Longitudinal wave A wave which the vibration of particles in the medium is parallel to the direction of the propagation of the wave Period, The time taken by a particle to make one complete oscillation or by a source to produce one complete cycle of wave Frequency, Number of complete oscillations made by a particle or number of cycles of wave produced by a source in one second Wavelength, Distance between two consecutive points in phase Wave speed, Distance travelled per second by a wave profile 5.2 External damping Oscillating system loses energy to overcome friction or air resistance Internal damping Oscillating system loses energy because of the stretching and compression of the vibrating particles in the system Damping Reduction in amplitude in an oscillating system due to loss of energy Resonance When a periodic force is applied to an oscillating system at its natural frequency 5.3 Wavefront Lines joining all the points of the same phase 5.4 Refraction of waves The change in direction of propagation of waves caused by the change in the velocity of waves when the waves propagate from one medium to another 5.5 Diffraction of waves The spreading of waves when the waves pass through a gap or round a barrier 5.6 Interference of waves The superposition of two or more waves from a coherent source of waves Constructive Interference Occurs when two crests or troughs are in superposition to produce maximum amplitude Destructive Interference Occurs when a crest and a trough are in superposition to produce zero combined amplitude 5.7 Electromagnetic spectrum Seven types of electromagnetic waves that forms a continuous spectrum Electromagnetic wave Produced when electric and magnetic field vibrate at right angle to each other Chapter 6 Light and Optics 6.1 Refraction of light A phenomenon when light changes direction when it travels from one medium to another medium of different densities Refractive index, The ratio of speed of light in vacuum to thespeed of light in medium Snell’s Law When light travels from one medium to another medium, the incident ray, the refracted ray and the normal meet at one point and are in the same plane 6.2 Total internal reflection When light travels from a medium with high optical density to a medium of low optical density Critical angle, Incident angle when refracted angle equal to 90° Formation of rainbow Caused by refraction,dispersion and total internal reflection when light passes through water droplets in air 6.3 Optical centre, Points at the centre of the lens Principal axis Straight line through the optical centre of a lens and the centre of curvature of both surfaces of the lens Axis of lens Straight line through the optical centre and perpendicular to the principal axis Focal point, Point located at the principal axis of a lens Object distance, Distance between object and optical centre of a lens Image distance, Distance between image and optical centre of a lens Focal length, Distance between focal point and optical centre of a lens Linear magnification, Ratio of image height to object height = ratio of image distance to object distance 6.6 Principal axis Straight line passing through the centre of curvature and pole of the spherical mirror Centre or curvature, Centre of sphere which produces a concave or convex mirror Radius of curvature of mirror, Distance between the pole of spherical mirror and the centre of curvature Focal point, A point on the principal axis of the spherical mirror Object distance, Distance between object and the pole of spherical mirror Image distance, Distance between image and the pole of spherical mirror Focal length, Distance between focal point and the pole of spherical mirror 128 Physics SPM | Physics
Form 5 Chapter 1 Force and Motion II 1.1 Resultant force, # The single force the represents the vector sum of two or more forces acting on an object 1.2 Resolution of forces Process of resolving a force into two components 1.3 Equilibrium of forces Forces acting on an object produce a zero resulting force 1.4 Elasticity The property of material that enables an object to return to its original shape and size afterthe force acting on it is removed Hooke’s law Extension of a spring is directly proportional to the force applied on the spring provided the elastic limit of the spring is not exceeded Chapter 2 Pressure 2.1 Pressure, Force per unit area 2.2 Atmospheric pressure, $%& Pressure due to the weight of the layer of air acting on the surface of the earth 2.3 Gas pressure The force per unit area exerted by the gas molecules as they collide with the wall of the container 2.4 Pascal’s principle Pressure applied on an enclosed fluid is transmitted uniformly in all direction in the fluid Hydraulic system A system that uses a liquid to transmit pressure 2.5 Buoyant force, ' Force acting upwards on an object immersed in a liquid when there is pressure difference between the lower surface and upper surface of the object Archimedes’ principle An object which partially or fully immersed in a fluid will experience a buoyant force equal to the weight of fluid displace 2.6 Bernoulli’s principle When the velocity of a fluid increases, the pressure in the fluid decreases and vice versa Chapter 3 Electricity 3.1 Electric field A region where electrical charges experience electric force Electric field strength, Electric force acting on a unit positive charge placed at a point Current, Rate of charge flow Potential difference, The work done to transfer one unit of charge across two points 3.2 Ohm’s law The potential difference across a conductor is directly proportional to the current that flow across the conductor Ohmic conductors Conductors that obey Ohm’s law Resistance, Ratio of the potential difference across the conductor to the electric current flowing through it Resistivity, The resistance per unit length of the material when its cross-sectional area is 1 m2 Superconductors Materials that conduct electricity without any resistance Critical temperature, The temperature when the resistivity of a superconductor becomes zero 3.3 Electromotive force, e.m.f. The energy transferred or work done by an electrical source to move one coulomb of charge in a complete circuit Internal resistance, The resistance caused by electrolyte in the dry cell 3.4 Electrical energy, The ability of the electric current to do work Electric power, The rate of electrical energy dissipated or transferred Chapter 4 Electromagnetism 4.1 Catapult field Resultant magnetic field produced by the interaction between the magnetic field from a current-carrying conductor and the magnetic field from a permanent magnet Magnetic field A region in the surrounding of a magnet which a magnetic material experiences a detectable force 4.2 Electromagnetic induction Production of an induced e.m.f. in a conductor when there is relative motion between the conductor and a magnetic field or when the conductor is in a changing magnetic field Induced current The current produced when there is the change in magnetic flux Lenz’s law The induced current always flows in a direction that opposes the change of magnetic flux that causes it Faraday’s law The magnitude of inducede.m.f. is directly proportional to the rate of cutting of magnetic flux 4.3 Transformer An electrical device which increases or decreases an alternating voltage based on the principle of electromagnetic induction Step-up transformer Transformer that is used to increase the voltage Step-down transformer Transformer that is used to decrease the voltage Ideal transformer Transformer that does not experience any loss of energy, that is the efficiency, is 100% 129 PhysicsAPPENDIX DEFINITION LIST
Chapter 5 Electronics 5.1 Thermionic emission Process of emitting electrons from a heated metal surface Cathode rays Beams of electrons moving at high speed in a vacuum 5.2 Semiconductor diode Electric component which allows electric current to flow in one direction only Rectification The process of converting an alternating current into a direct current Full-wave rectification Process where both halves of every cycle of an alternating current is made to flow in the same direction 5.3 Transistor An electronic component that has three terminals, namely emitter, base, and collector Chapter 6 Nuclear Physics 6.1 Radioactive decay Process in which an unstable nucleus becomes more stable by emitting radioactive radiation Alpha particle, Helium nucleus which consists of two protons and two neutrons Beta particle, A fast-moving electron (negative) Gamma rays, High-frequency electromagnetic wave (neutral) Half-life, ! " The time taken for a sample of radioactive nuclei to decay to half of its initial number Activity, Number of decays per second / Number of radioactive particles emitted per second 6.2 Nuclear energy Atomic energy,released during nuclear reactions such as radioactive decay, nuclear fission and nuclear fusion Nuclear fission Nuclear reaction when a heavy nucleus splits into two or more lighter nuclei while releasing a large amount of energy Nuclear fusion Nuclear reaction in which small and light nuclei fuse under extremely high temperature and pressure to form a heavier nucleus while releasing a large amount of energy. Chain reaction A self-sustaining reaction in which the products of a reaction can initiate another similarreaction Chapter 7 Quantum Physics 7.1 Black body An idealised body that is able to absorb all electromagnetic radiation that falls onit Thermal radiation Electromagnetic radiation that includes visible light and radiation that cannot be seen by the human eyesuch as infrared radiation Quantum of energy Discrete energy packet and not a continuous energy Photon Light energy that is transmitted in the form of energy packet 7.2 Photoelectric effect Emission of electrons from metal surface when illuminated by a beam of light at certain frequency. 7.3 Work function, Theminimum energyrequiredfora photoelectrontobeemittedfroma metal surface Threshold frequency, ( The minimum frequency for photoelectric effect to occur 130 Physics SPM | Physics