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IGCSE Waves in a nutshell
1. Waves carry energy not matter and pass it on by oscillating particles.
2. In transverse waves the oscillations are at right angles to the wave eg electromagnetic waves,
water waves, in longitudinal waves the oscillations are parallel to the wave eg sound and
3. Frequency is the number of waves/sec, amplitude is the maximum displacement of a particle
and wavelength is the distance from one wave crest to the next.
4. Frequency = 1/time period
5. Wave speed = frequency x wavelength
6. Waves can be reflected the angle of incidence = the angle of reflection
7. Light is slowed down and refracted when it enters a denser material. refractive index = sin i /
8. Light may be totally internally reflected along a glass fibre if it hits the internal boundary at
greater than the critical angle, c refractive index = 1 / sin c
9. Waves can be diffracted through gaps or when they pass an edge. The extent of diffraction
depends on the wavelength and the physical dimension of the gap
10. All electromagnetic waves are transverse and travel at the same speed in a vacuum
11. The electromagnetic waves in order of increasing frequency are: radio, microwave, infrared,
light, ultraviolet, X ray, gamma
12. Radio waves are used for communication, microwave for mobile phones and cooking,
infrared for remote controls, burglar alarms and night-time photography, light for
photography, vision, sending signals along optical fibres, ultraviolet for sun tanning,
reflecting off ink that cannot be seen in visible light, X rays for taking photographs of bones,
gamma for radiotherapy and medical diagnosis.
13. There are dangers from exposure to radiation, internal heating by microwaves, burns by
infrared, damage to skin and eyes by ultraviolet, cell damage by X ray and gamma
IGCSE Sound and digital signals in a nutshell
1. Digital signals are carried as a series of 1 & 0 whereas analogue signals are continuously
varying. Digital signals are less susceptible to noise so are clearer.
2. Ultrasound (frequency higher than 20kHz) is used for medical imaging and depth sounding by
3. The loudness of a sound depends on the amplitude of vibration
4. The pitch of a sound depends on the frequency of vibration
5. The speed of sound in air can be measured by a simple direct method of distance and time
6. Describe how an oscilloscope and microphone can be used to display a sound