Cambridge IGCSE Physics Chapter 14 Properties Of Waves Rev. Notes - SpyAgent 1687

Chapter 14: Properties of waves (REVISION NOTES)

REVISION NOTES

 Ripple is a small uniform wave on the surface of water.
 Ripple is caused by disturbance on a steady object.
 Sound is caused by vibration; disturbance in air.
 Sound  3 instruments: String  Percussion  Wind.
 Crest (also known as the peak) is the highest point of the wave.
 Trough is the lowest point of the wave.

 Amplitude is the distance between the crest and the mean
position.

OR

 Amplitude is the greatest height (crest) or depth (trough) of a wave
from its undisturbed position/level.

 Frequency is how sharp/shrill the voice is; the pitch.
 Time Period is simply the time it takes to complete one oscillation.
 Amplitude is measured in metres, m, or centimetres, cm, but the

S.I. unit is considered to be metres.
 Frequency is measured in hertz, Hz; the actual unit is considered

to be nu, ν, but we measure it in Hz.
 Time Period is measured in seconds, s.
 No. of waves / sec = Hz
 Sound has 2 types: Transverse and Longitudinal.
 Transverse wave is a wave in which the vibration is at right angles

to the direction of propagation of the wave.
 Longitudinal wave is a wave in which the vibration is forward and

back, parallel to the direction of propagation of the wave.

 Seismic waves are waves caused by earthquakes.

 P-waves are fast moving, longitudinal seismic waves.

 S-waves are slow moving, transverse seismic waves.

 Wavelength, measured in metres (m), is the distance between two

adjacent crests or troughs of a wave.

 Wavelength is represented by the symbol lambda, λ.

 Decibel is the loudness of sound.

 Wave speed is the speed at which a wave travels.

 v =



 v = λ = fλ  v = λ × 1 f = 1 ; f = . T = 1

T

 Frequency ∝ 1

ℎ

 Higher the amplitude – Higher the loudness of sound

 As wavelength increases, frequency decreases.

 As wavelength decreases, frequency increases.

 Wave is divided into two main categories:
Mechanical and Electromagnetic

 Mechanical wave is a wave which need material medium to travel.
 Electromagnetic wave requires no medium.

 Mechanical wave is divided into Transverse and Longitudinal.
 T.W.  energy direction particle vibrationperpendicular
 L.W.  energy direct & particle vibrationparallel
 L.W. (eg) : sound – providing energy to one particle...

It will go ahead & transfer energy to another particle & come back.
Particles are moving in the same direction as the energy.

Position

Comes back to the Time
same position

 Compression – high particle density
 Rarefaction – low particle density

Q. Why are all things transparent?

A. A material appears transparent when it does not strongly absorb or
diffract light. As far as the absorbance of a solid goes, you pretty much
have to take what Nature gives you. Diffraction, however, can be
influenced by how the material is prepared.

 v = λf – f = constant (in all medium), λ = decreases v = decreases
(λ and v – this is when going in higher density medium).

 As material density increases, velocity of light decreases.

Reflection of ripples

 Wavefront is a line joining adjacent points on a wave that are all in
step with each other.

 Law of reflection:
angle of incidence = angle of reflection

Refraction of ripples

Q. Is light a particle or a wave?
A. Both.

 Diffraction is when the light/wave bends at the corners.
 Diffraction is when a wave spreads out as it travels through a gap

or past the edge of an object.
 A small opening through which light passes is called a slit; light

spreads out.
 Eg: torch  it passes sideways and spreads out  doesn’t travel

in a straight line.

 Mixing of the waves is called interference.