BSL Physics Glossary - electromagnetic spectrum - definition
At one end of the electromagnetic spectrum there are waves with short wavelengths. At the other end there are waves with longer wavelengths. In the central area of the spectrum is visible light, which we, humans, can see. We can't see the light on either side of the visible part of the spectrum. Starting from the shortest wavelengths, first there are gamma rays, then X-rays, then ultra-violet light. Then there are the visible colours starting with violet and blue, right through to red. Next there are infra-red, microwaves and radio waves. What is the speed of the waves on this electromagnetic spectrum? All these waves travel at the same speed as the speed of light.