Question

In YDSE $S_1$ and $S_2$ has intensity $I$ and $9I$ respectively. Find difference in intensity between points which has phase difference of $\pi /2$

• A. 10 I
• B. 6 I
• C. 8 I
• D. 4 I

Answer 1

Answer: (B)

Solution For Phase difference $\pi /2$
$I=I_1+I_2+2\sqrt{I_1{I}_2}\cos \varphi$
$=I+9I+2\sqrt{I9I}\cos \pi /2$
$=101$
For Phase difference $\pi$
$|=|+9|-6|=4\mid$
Difference in intensity $=10I-4I=6I$