Question

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

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

Interference is a phenomenon in which two waves super impose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either
because they come from the same source or because they have nearly same frequency. Option C satisfies the above conditions.