Optics Question 146
Question: In the ideal double-slit experiment, when a glass-plate (refractive index 1.5) of thickness t is introduced in the path of one of the interfering beams (wavelength l), the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass-plate is
[IIT-JEE (Screening) 2002]
Options:
A) 2l
B) $ \frac{2\lambda }{3} $
C) $ \frac{\lambda }{3} $
D) l
Show Answer
Answer:
Correct Answer: A
Solution:
According to given condition $ (\mu -1)t=n\lambda $ for minimum t, n =1
So, $ (\mu -1){t _{\min }}=\lambda $
$ {t _{\min }}=\frac{\lambda }{\mu -1}=\frac{\lambda }{1.5-1}=2\lambda $
