Question

The intensity ratio of two coherent sources of light is $P$. They are interfering in same region and produce interference patter. Then the fringe visibility is.

• A. $\frac{1+P}{2\sqrt{P}}$
• B. $\frac{2\sqrt{P}}{1+P}$
• C. $\frac{P}{1+P}$
• D. $\frac{2P}{1+P}$

Answer 1

The correct option is B $\frac{2\sqrt{P}}{1+P}$

Visibility, $V=\frac{I_{max}-I_{min}}{I_{max}+I_{min}}=\frac{2\sqrt{I_1{I}_2}}{(I_1+I_2)}$
$=\frac{2\sqrt{I_1/I_2}}{\frac{I_1}{I_2}+1}=\frac{2\sqrt{P}}{P+1}$