Question

Which one of the following statements is incorrect about laser?
(A) It is a technique for producing intense beams of visible light, ultraviolet or infrared radiation of different wavelengths.
(B) Laser beams can drill a hole, even in a diamond.
(C) A variety of lasers are made from solids like the ruby crystal semiconducting materials, liquids and gases.
(D) All waves in laser travel in different phase.

Answer 1

In order to solve this question, we should know that Laser is a collective term used to describe Light amplification by stimulated emission of radiation. Here we will discuss about basic properties of laser according to the given four statements and later figure out which statement is incorrect about laser.

Complete Step By Step Answer:
In physics, Laser is an electrical device which is used to produce highly intense light through optical amplification process.
So, Laser is simply a technique to produce intense beam of light, either it may consist of visible light such as red, blue or ultraviolet and infrared radiations too. so statement of option (A) is correct statement.
In mid $1960$ laser was first used to dig a hole in diamond which create a hole of diameter about $0.2mm.$ So, option (B) is also correct statement.
Ruby laser is a common example indicating that a variety of lasers are available and made of different solids. So, option (C) is also correct statement.
All waves in a laser must be in same phase in order to increase their intensity so, all the waves must be in same phase, if they were in out of phase the net intensity will not be maximum. So, All wave in laser travel in same phase, which shows option (D) All waves in laser travel in different phase is incorrect one.
Hence, the correct option is (D) All waves in laser travel in different phase.

Note:
It should be remembered that, net intensity of two waves is maximum if they are in same phase which means phase difference between two waves is ${0^o}$ and this result in maximum intensity which helps the laser to produce high intense light.