The Electromagnetic Spectrum

Light is only one type of electromagnetic radiation. We have seen that white light can be dispersed to show the different colours of the visible spectrum. Each colour has its own frequency (and wavelength for a given speed) and is refracted by a different amount accordingly. is refracted the least and light the most.

The colours that are refracted the least have the lowest frequencies (and the longest wavelengths). The colours in order are: , , , , , and .

All types of EM wave travel at the same speed, 300,000,000 m/s in a . The various types of EM radiation form a continuous spectrum extending far beyond each end of the visible spectrum (frequencies our eyes happen to be able to detect). Different wavelengths of EM radiation are reflected, absorbed or transmitted differently by different substances and types of surfaces.

The energy an EM wave carries can do a number of things. It makes substances that absorb it hotter, or it may induce an alternating current in a conductor with the same frequency as the wave itself. The higher the frequency the higher the energy of the wave.

The uses, effects and naming of different types of EM radiation depend on these and other properties of the wave.

Lowest Frequency		Lowest Energy
Highest Frequency		Highest Energy