Optics Question 1075
Question: In the Young’s double slit experiment, the ratio of intensities of bright and dark fringes is 9. This means that
[IIT 1982]
Options:
A) The intensities of individual sources are 5 and 4 units respectively
B) The intensities of individual sources are 4 and 1 units respectively
C) The ratio of their amplitudes is 3
D) The ratio of their amplitudes is 2
Show Answer
Answer:
Correct Answer: B
Solution:
$ \frac{{I _{\max }}}{{I _{\min }}}=9\Rightarrow {{( \frac{a _{1}+a _{2}}{a _{1}-a _{2}} )}^{2}}=9\Rightarrow \frac{a _{1}+a _{2}}{a _{1}-a _{2}}=3 $
$ \Rightarrow \frac{a _{1}}{a _{2}}=\frac{3+1}{3-1}\Rightarrow \frac{a _{1}}{a _{2}}=2. $
Therefore $ I _{1}:I _{2}=4:1 $
