OCR - P1: Radiation and waves

P1.3 How do waves behave?
Background to the topic What you should be able to do:

A wave is a regular disturbance that transfers energy in the direction that the wave travels, without transferring matter.

For some waves (such as waves along a rope), the disturbance of the medium as the wave passes is at right-angles to its direction of motion. This is called a transverse wave.

For other waves (such as a series of compression pulses on a slinky spring), the disturbance of the medium as the wave passes is parallel to its direction of motion. This is called a longitudinal wave. The speed of a wave depends on the medium it is travelling through. Its frequency is the number of waves each second that are made by the source. The wavelength of waves is the distance between the same points on two adjacent disturbances.

The ways in which light and sound waves reflect and refract when they meet at an interface between two materials can be modelled with water waves.

A wave model for light and sound can be used to describe and predict some behaviour of light and sound.

1. Describe wave motion in terms of amplitude, wavelength, frequency and period

2. Describe evidence that for both ripples on water surfaces and sound waves in air, it is the wave and not the water or air itself that travels

3. Describe the difference between transverse and longitudinal waves

4. Describe how waves on a rope are an example of transverse waves whilst sound waves in air are longitudinal waves

5. Define wavelength and frequency

6. Recall and apply the relationship between speed, frequency and wavelength to waves, including waves on water, sound waves and across the electromagnetic spectrum:
wave speed (m/s) = frequency (Hz) × wavelength (m)

7. a) describe how the speed of ripples on water surfaces and the speed of sound waves in air may be measured.
b) describe how to use a ripple tank to measure the speed/frequency and wavelength of a wave

8. a) describe the effects of reflection and refraction of waves at material interfaces
b) describe how to measure the refraction of light through a prism.
c) describe how to investigate the reflection of light off a plane mirror.

Refraction of light and sound can be explained by a change in speed of waves when they pass into a different medium;

A change in the speed of a wave causes a change in wavelength since the frequency of the waves cannot change, and that this may cause a change in direction.

9. Recall that waves travel in different substances at different speeds and that as these speeds vary the wavelength varies

10. Explain how refraction is related to differences in the speed of the waves in different substances

11. Recall that light is an electromagnetic wave

12. Recall that electromagnetic waves are transverse