Vapour lamps and discharge tubes produce light with a dominant colour. For example, the sodium vapour lamp produces a yellow/orange glow, which is due to light of wavelength 590nm. Other wavelengths of light are also emitted from a sodium vapour lamp but the colour due to light of wavelength 590nm is much more intense that any other colour. A sodium vapour lamp is in effect a monochromatic light soucre, because its spectrum is dominated by light of a certain colour.
Lights from a filament lamp or from the Sun is composed of the colours of the spectrum and therfore covers a continuous range of wavelengths from about 350nm to about 650nm. If a beam of white light is directed at a colour filter, the light from the filter is a particular colour because it contains a much narrower range of wavelengths than white light does.
Light from a laser:
- Laser light is highly monochromatic, which means we can specify its wavelength to within a nanometre. The wavelength depends on the…