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The electromagnetic spectrum is a family of transverse waves. These waves have a side-to-side motion and they all travel at the same speed but vary in frequency and wavelength. Frequency is the number of waves that pass a point in one second. Light that we use to see with (visible light) is a very small part of this spectrum. The different colours we see in light are due to differences in wavelength. The highest frequency waves have the shortest wavelength and are known as gamma waves, which are used in medicine. The longest, lower frequency waves are used for TV and radio communication. Infrared waves are used in night vision cameras and remote controls.