Amplitude is the height of a wave from the undisturbed or normal position to its crest. As the amount of energy within a wave is increased, then the amplitude also increases. Although sound and light waves are different (sound waves are longitudinal waves and light waves are transverse waves), it is possible to illustrate how they react to increased energy levels. An increase in sound energy is indicated by the volume or loudness of that sound: the greater the level of sound energy that is put into a sound, the louder the sound will be. The same applies to light: the more energy there is in light, the greater the intensity or brightness of the light. Therefore, a sound wave that has high amplitude is a louder sound. Likewise, a light wave with high amplitude is a brighter light. We cannot ‘see’ the waves but by using measuring instruments (e.g. an oscilloscope), the amplitude of a sound wave can be shown on screen. The amplitude of a wave then is described as the extent to which the wave reaches from the normal.