NEET Solved Paper 2019 Question 36
Question: In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be $ 0.2{}^\circ $ . What will be the angular width of the first minima. If the entire experimental apparatus is immersed in water? $ ({\mu _{water}}=4/3) $ [NEET 5-5-2019]
Options:
A) $ 0.05{}^\circ $
B) $ 0.1{}^\circ $
C) $ 0.266{}^\circ $
D) $ 0.15{}^\circ $
Show Answer
Answer:
Correct Answer: D
Solution:
$ \theta \propto \lambda $
$ {\lambda_1}=400nm,{\theta_1}=0.2{}^\circ ,{\mu _{water}}=4/3 $
$ \frac{{\theta_1}}{{\theta_2}}=\frac{{\lambda_1}}{{\lambda_2}}\mu =\frac{c}{v}=\frac{{\lambda_1}}{{\lambda_2}}=\frac{4}{3} $
$ \frac{{\theta_1}}{{\theta_2}}=\frac{4}{3} $
$ {\theta_2}=\frac{3}{4}({\theta_1}) $
$ =\frac{4}{3}(0.2{}^\circ )=0.15{}^\circ $
