WAVES SUMMARY

THERE ARE TWO TYPES OF WAVE

• The particles move at right angles to the direction of the wave (e.g light)
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• Longitudinal
• The particles move along the direction of the wave (e.g sound)

PROPERTIES OF WAVES

• Amplitude;
• The maximum distance of the particle from its resting position
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• Longitudinal ;
• The distance between to corresponding points in two consecutive waves

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• How many waves are completed in one second ( measured in hertz)
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• Period;
• How long it takes for one complete wave to be produced ( measured in seconds)

THE WAVE EQUATION

THE WAVE EQUATION

• There is a relationship between the;
• Wavelength
• The frequency
• The wave speed

THE WAVE EQUATION

• Frequency
• Wavelenght
• Wave speed, V=frequency,(f) X wavelenght,
• V= F lambda

REFLECTION

REFLECTION

• Reflection occurs when waves strike an opaque surface
• We know that the angle of incidence and the angle of reflection are equal.
• angle of incidence = angle of reflection

REFRACTION

REFRACTION

• Refraction occurs when waves move from one medium to another
• When travelling from a less dense to a more dense medium, the ray moves towards the normal
• When moving from a more dense to a less dense medium the ray moves away from the normal
• This occurs because the wavelength become shorter

DIFFRACTION

DIFFRACTION

• When waves go through a large gap, the diffraction is very large
• You should know;
• All waves can be reflected, refracted and diffracted

THE ELECTROMAGNETIC SPECTRUM

ELECTROMAGNETIC SPECTRUM

• The electromagnetic spectrum is made up of transverse waves
• They all transfer energy
• They are all transverse waves
• They all travel at the speed of light
• They can all be reflected, refracted, defracted

HOW TO REMEMBER IT

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DIFFERENT WAVES

RADIO WAVES

• Used mainly in communications and navigation signals
• They have the lowest frequency
• The longest wavelength

MICROWAVES

• They cook you from the inside out
• Can be used in satellite communications and radar

INFRA-RED

• Mainly used in heating (domestic & cooking)
• Security cameras (night vision equipment
• Used in remote controls
• Can be dangerous because they can cause sunburn

VISIBLE LIGHT

• Detectable by human eyes
• Used in photography and fibre optic cables (transfer information)

ULTRAVIOLET

• Used in fluorescent lighting
• Sterilising water, money scanners
• Causes cancer and damage to the eyes
• Some insects can detect it (bees)

X-RAYS

• Used to produce pictures of the insides of body's
• Dangerous because they can cause cell mutation and cancer

GAMMA RAYS

• Used in treatment of some cancers
• Sterilisation of hospital equipment & food
• Cause cell mutation and cancer

YOU SHOULD KNOW

• Radio waves & Ultraviolet waves
• Microwaves & X-Rays
• Infa-red waves & Gamma rays
• Visible light

LIGHT

LIGHT

• Light is a transverse wave, so can be;
• Reflected
• Refracted
• Diffracted
• The speed of light is 300 000 000 m/s

REFLECTED IMAGES

• The images produced in a plane mirror has certain properties
• The image is as far behind the mirror as the object is in front
• The image is the same size as the object
• The image is virtual - cannot be produced on a screen
• The image is laterally inverted ( back to front)

USES OF REFLECTION AND REFRACTION

• Periscopes, reflecting telescope, SLR cameras
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• Refraction
• Binoculars and lenses (glasses & telescopes)

REFRACTIVE INDEX

REFRACTIVE INDEX

• Refractive index (n) = sin i / sin r
• (where i is the angle of incidence and r is the angle of reflection)
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• The refractive index can also be calculated using the critical angle
• n = 1 / sin c

USES OF TIR

• Prismatic periscope
• Reflectors
• Fibre optics
• Endoscope

SOUND

SOUND WAVES ARE MADE UP OF;

• Compressions (where the particles are very close together)
• Rarefactions (where the particles are more spread out)
• These sound waves cause the ear drum to vibrate
• These vibrations are changed into electrical signals by the cochlea
• These are detected by the brain

FREQUENCY AND AMPLITUDE

FREQUENCY AND AMPLITUDE

• Small objects vibrate quickly and produce high frequency sounds
• Large objects vibrate slowly, producing lower frequency sounds
• The frequency of a source is;
• The amount of complete vibrations it makes each second
• Measured in hertz (Hz)

FREQUENCY AND AMPLITUDE

• How to find the frequency of a sound wave
• You can do this using a Cathode Ray Oscilliscope
• CRO
• Frequency = 1 / period

YOU SHOULD KNOW

• The greater the amplitude of the vibration, the louder the sound
• The higher the frequency of the vibration, the higher the pitch
• Sounds with very high frequencies are called ultrasounds

ANALOGUE & DIGITAL

ANALOGUE & DIGITAL

• Information has to be converted into and electric signal
• These signals can be sent down a telephone wire;
• Or transmitted as an EM wave;
• The signals can be analogue or digital

ANALOGUE AND DIGITAL SIGNALS

• Analogue signals can take any value within a certain range
• the amplitude and frequency of the signal can vary continuously

ADVANTAGES OF DIGITAL

• Whenever you send a signal a long distance the signal weakens
• The signals may also pick up interference or noise;
• This comes from electrical disturbances or other signals.
• Whenever you amplify an analogue signal;
• The noise is amplified as well so the signal will lose quality

ADVANTAGES OF DIGITAL

• This comes from electrical disturbances or other signals.
• With a digital signal, the noise can be ignored so the signal remains high quality at the receiver.