Electromagnetic spectrum

The electromagnetic spectrum describes the range of radiation that exists physically. This covers radio, infrared, ultraviolet, x-rays, gamma rays, and visible light (which is a small subset of the spectrum). From left to right, we have waves with the longest wavelengths (and lowest energy) to the shortest wavelengths (and highest energy).

• Visible light falls between 400 and 700 nm.

Energy in the electromagnetic spectrum is quantised and proportional to its wavelength:

$$E=\frac{hc}{\lambda }$$

where $h=6.626\times 10^{-34}J$, Planck’s constant, $c=3\times 10^{8}m{s}^{-1}$, the speed of light in a vacuum, and $\lambda$ is the wavelength. Alternatively:

$$E=hf$$

where $f$ is the frequency of the wave.