Light is a powerful energy which is made up of wavelengths ranging from very short gamma rays to very long radio waves. The human eye has evolved to detect wavelengths between 400nm and 700nm as colour. We see this as the rainbow ranging from blue through to red light. We do not see UV wavelengths which range up to 390nm and at the other end of the electromagnetic spectrum, we do not detect Near Infrared wavelengths at around 800nm plus. NIR is a very powerful wavelength even though we cannot see it.