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 $

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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 $