Two sources of light are said to be coherent when they emit light of

A. same wavelength
B. same amplitude
C. same intensity
D. constant phase difference

Choose the correct answer from the options given below:

A and D only

The correct answer is Option (2) → A and D only

Two sources of light are said to be coherent when they emit light of the same frequency (or same wavelength) and have a constant phase relationship.