Our view of the sky at night is possible because of the emission and reflection of light. 'Light' is the better-known term for the electromagnetic spectrum, which includes waves in the visible, ultra-violet, infra-red, microwave, radio, X-ray and gamma-ray regions. The scale of the spectrum is so large that no region is distinct, several overlap each other.
Each of these regions in the electromagnetic spectrum represent transverse waves, travelling as electrical and magnetic fields which interact perpendicularly to each other, with different ranges of wavelength. The magnetic field oscillates vertically and the electric field horizontally, and each field induces the other.
By the end of the nineteenth century, Maxwell gave a realistic value for c, the speed of light:
c = __1__ = 3 x 108 ms-1
The relationship between the speed of all electromagnetic radiation, wavelength (l) and frequency (f) is shown to be c...