Electromagnetic Spectrum

The sun emits radiation in a broad spectrum called the electromagnetic spectrum, a small portion of which is visible. The visible spectrum can be seen when cloud droplets separate light in a rainbow. The visible spectrum is red, orange, yellow, green, blue, indigo and violet. Ultraviolet (UV) Radiation is outside of the visible range near violet, hence the name.

A glass prism can be used to split white light into separate colours that are sensitive to the human eye, ranging from red (longer wavelength) to violet (shorter wavelength). The human eye cannot detect electromagnetic radiation outside this range.