Question

In YDSE $S_{1}$ and $S_{2}$ has intensity $I$ and $9 I$ 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 $\pi / 2$
$I=I_{1}+I_{2}+2 \sqrt{I_{1} I_{2}} \cos \phi$
$=I+9 I+2 \sqrt{I 9 I} \cos \pi / 2$
$=101$
For Phase difference $\pi$
$|=|+9|-6|=4 \mid$
Difference in intensity $=10I-4I=6I$