Question

Two sources of light are said to be coherent, when they give light waves of same

• A. amplitude and phase
• B. wavelength and constant phase difference
• C. intensity and wavelength
• D. phase and speed

Answer 1

Answer: (B)

wavelength and constant phase difference

In physics, two wave sources are perfectly coherent if they have a constant phase difference and the same frequency (amplitude may be different).

As $c$ be the speed of light which is constant.

Using, $c=\nu \lambda$

Now same $\nu$ gives same $\lambda .$ for the two light sources.

Example: $y_1=A_{1}sinwt$ and $y_2=A_{2}sin(wt+\varphi )$ where $\varphi$ is constant.