Question

The necessary condition for an interference by two sources of light is that

• A. two light sources must have the same wave length
• B. two point sources should have the same amplitude and same wavelength
• C. two sources should have the same wave, length, nearly the same amplitude and have a constant phase difference
• D. two point sources should have a randomly varying phase difference

Answer 1

Answer: (C)

Two sources should have the same wavelength, nearly the same amplitude and have a constant phase difference. If the phase difference between two interfering waves does not remain constant, interference pattern will not be Sustained.