This programme uses everyday examples, laboratory demonstrations and graphics to illustrate and explain the nature and properties (including reflection and refraction) of waves, particularly in light and sound.

The programme is divided into three sequences:

1. Introduction to Waves
2. Reflection
3. Refraction

It could be used at any stage in the teaching of waves, light or sound. It would make an excellent summary or revision aid. It could be shown in full or in selected sections.

Introduction to Waves

00.00 Introduction to some waves

Waves - whether in the sea, light, earthquakes or the Tacoma Narrows Bridge - carry energy.

00.55 A wave carries energy without the medium being permanently displaced

A water wave seems to move from right to left, but a float on the water simply goes up and down, not right to left.

01.27 Models of transverse waves

Sequences of water waves, and a transverse wave made of moving dots. One dot is orange and can be seen to move up and down while the wave moves across. The particle's movement is at right angles to the wave's motion.

02.09 What is wavelength?

Graphics are used to pick out the wavelengths of two different transverse waves.

02.32 What is frequency?

Graphics are used to illustrate the frequency of a wave and how it affects the wavelength.

02.52 Longitudinal waves

A longitudinal wave is made in a spring. The movement of the particles is along the direction of the wave; again, the particles are not left permanently displaced once the wave has passed. An example is a sound wave.

03.39 Earthquake waves

Earthquakes make both longitudinal and transverse waves which travel around and through the Earth.

Reflection

04.12 Reflection of billiard ballsThe movement of billiard balls is used to illustrate the laws of reflection, including a definition of the normal.

04.54 Reflection of waves

Waves are made in a ripple tank and projected onto the floor, showing the wave fronts. The reflected wave fronts are highlighted using graphics.

05.54 Making virtual images using reflection

A 'magic trick' is used to illustrate the production of a virtual image in a piece of glass. Graphics are used to show the position of the image and how it is produced by the reflection of light. This is a version of Pepper's Ghost - an optical illusion.

06.59 Echo sounding at sea

Fishermen and sailors use echoes of sound waves to calculate the depth of the sea. A printout of the echoes shows the depth of the sea and any fish in the water. This is explained with some simple graphics.

07.47 Echolocation and ultrasound scans

Bats also use echoes of ultrasound to determine their position in dark caves. The same principle is used to make images of unborn babies safely.

08.15 Parabolic reflectors

Parabolic reflectors focus a wave and are used to collect signals from satellites. The behaviour of a parabolic reflector is demonstrated by focusing infra-red waves onto a match head to light it.

Refraction

09.34 Simple refraction

A clear demonstration of light bending as it passes through a glass block.

10.10 Refraction of water waves

Water waves in a ripple tank are refracted when they slow down. The bending of the waves is highlighted with clear graphics.

11.00 Explaining refraction

A graphic of a truck driving into some marshy ground explains why waves change direction when they slow down.

11.18 Some effects of refraction

A bent pencil looks straight when it is put in water and a straight pencil looks bent. When the light is refracted the eye is tricked. This is explained using simple optics.

12.23 Total internal reflection

A clear laboratory demonstration of total internal reflection inside a glass block.

13.01 Optical fibres

Two nice demonstrations of total internal reflection of light along tubes. Firstly, a beam of light is sent down a curved perspex rod using total internal reflection. Secondly, a laser beam is bounced down a stream of running water. Both demonstrations illustrate the principle of operation of an optical fibre.