Question

The max. intensity produced by two coherent sources of intensity $I_2$ and $I_2$ will be

• A. I${}_1+I_2$
• B. $I_1^2+I_2^2$
• C. $I_1+I_2$ + 2$\sqrt{I_1{I}_2}$
• D. zero

Answer 1

Answer: (C)

$I_1+I_2$ + 2$\sqrt{I_1{I}_2}$

As R${}^2$ = a${}^2$ + b${}^2$ + 2 ab cos $\varphi$
$\therefore$ I${}_{max}$ = I${}_1$ + I${}_2$ + 2$\sqrt{I_1{I}_2}$ cos 0${}^o$
= I${}_1$ + I${}_2$ + 2$\sqrt{I_1{I}_2}$