Light is produced in 4 main ways.
LASER: LASER stands for Light Amplification
by Stimulated Emission of Radiation and is coherent and polarised. It has a
narrow bandwidth.
LED: Light Emitting Diodes produce
light when electricity passes through a microchip. Can be monochromatic or
multiple.
Incandescent: Incandescent bulbs
heat up a coil which causes it to glow and release light. This light is not
coherent and not polarised and is mainly infrared light.
Synchrotron: Produce light from
accelerating charged particles through magnetic fields. Is polarised however
has a range of wavelengths and is not coherent.