Question 10: What is meant by the statement that a laser beam is coherent, monochromatic and parallel?
Lasers are Coherent
When we say a laser beam is coherent we mean to say that laser waves are in step. If one ray is placed over the other, the crests of one ray will exactly coincide with the crests of the other ray and the troughs of one ray will exactly coincide with the troughs of the other ray.
Lasers are Monochromatic
By monochromatic we mean all the photons have the same wavelength. Hence lasers have one color and said to be monochromatic.
Lasers are Parallel
By parallel we mean the laser beam is unidirectional. All radiations travel in one specific direction.
Hence we say that a beam of lasers is coherent, monochromatic and parallel.