P1.5 Waves

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P1.5 Waves

Wave basics


  • The amplitude is the displacement (the shortest distance) from the rest position to the crest
  • The wavelength is the length of a full cycle of the wave eg crest to crest or trough to trough
  • Frequency is the number of complete waves passing a certain point per second OR the number of complete waves produced per second
  • Frequency is measured in Hertz (Hz) 
  • 1 Hz is 1 wave per second
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P1.5 Waves

Wave basics

Slinky spring demo        


  • Transverse waves (a) have sideways vibrations - the vibrations are at 90 degrees to the direction of energy transfer of the wave
  • Light is an example of a transverse wave
  • Longitudinal waves (b) have vibrations along the same line - the vibrations are parallel to the direction of energy transfer of the wave
  • Sound, ultrasound and shock waves are examples of longitudinal waves
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P1.5 Waves

Wave formula


Example: A radio wave has a frequency of 92.2 X 10   Hz. Find its wavelength. The speed of all radio waves is 3 X 10   m/s

Solution: wavelength = velocity / frequency

                              = 3 X 10   / 92.2 X 10

                              = 3.25m

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P1.5 Waves



Angle of incidence = Angle of reflection

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P1.5 Waves

The image formed in a plane mirror


The image formed in a plane mirror is:

  • the same size as the object
  • as far behind the mirror as the object is in front
  • virtual (cannot be projected on to a screen)
  • upright
  • laterally inverted (right side of object appears to be the left side of the image and vice versa
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P1.5 Waves

Diffraction of waves


  • The amount of diffraction depends on the size of the gap relative to the wavelength of the wave
  • The narrower the gap or the longer the wavelength, the more the wave spreads out
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P1.5 Waves


  • As the light passes from air into glass it bends (refracts) towards the normal
  • As the light passes from glass to air it bends (refracts) away from the normal
  • Waves are only refracted if they meet at an angle
  • If they are travelling along the normal (the angle of incidence is zero) they are not refracted
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P1.5 Waves

Electromagnetic Spectrum


  • EM waves with different wavelengths (or frequencies) have different properties
  • All the different types of EM wave travel at the same speed in a vacuum
  • EM waves with higher frequencies have shorter wavelengths
  • Different EM waves have different properties and therefore different uses
  • EM waves have different uses for communication because of their different wavelenths
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P1.5 Waves

Radio waves are used mainly for communication


  • Long wavelength radio waves diffract around the curved surface of the Earth. They can also get around hills and into tunnels
  • Short wave radio signals can be received at long distances from the transmitter. This is because they are reflected by the Earths electrically charged upper atmosphere, the ionosphere (diagram)
  • To receive TV and FM signals, there must be nothing between the aerial and the transmitter - the signal will not bend around hills or travel far through buildings
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P1.5 Waves

Microwaves are used for satellite communications and mobile phones


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P1.5 Waves

Infrared waves are used for remote controls


Remote controls work by emitting different patterns of infrared waves to send different instrutions to an appliance

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P1.5 Waves

Visible light is used for photography


  • Cameras use a lens to focus visible light onto a light-sensitive film or electronic sensor
  • The lens aperture controls how much light enters the camera
  • The shutter speed allows you to control how long the film or sensor is open to the light
  • The longer the film or sensor is open to the light, the more light that will enter the camera and react with the film
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P1.5 Waves

Sound travels as a wave


  • Sound waves are caused by vibrating objects
  • The vibrations are passed through the surrounding medium eg air as a series of compressions
  • Sound waves are a type of longitudinal wave
  • Sound cannot travel in a vacuum (no particles)
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P1.5 Waves

The high the frequency, the higher the pitch



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lisa linsdell

A really good set of revision notes to support this AQA unit. Includes diagrams to help aid understanding.


i angery 

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