Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber. • Electromagnetic waves form a continuous spectrum and all types of electromagnetic wave travel at the same velocity through a vacuum (space) or air. • The waves that form the electromagnetic spectrum are grouped in terms of their wavelength and their frequency. Going from long to short wavelength (or from low to high frequency) the groups are: radio, microwave, infrared, visible light (red to violet), ultraviolet, X-rays and gamma rays. • Our eyes only detect visible light and so detect a limited range of electromagnetic waves. • Students should be able to give examples that illustrate the transfer of energy by electromagnetic waves.