NEET Solved Paper 2014 Question 35
Question: A beam of light of $ \lambda $ = 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is [AIPMT 2014]
Options:
A) 1.2 cm
B) 1.2 mm
C) 2.4 cm
D) 2.4 mm
Show Answer
Answer:
Correct Answer: D
Solution:
From the figure, $ \tan \theta =\frac{x/2}{2} $ For small $ \theta $
and when $ \theta $ is counted in rad, $ \tan \simeq \theta $
So, $ \theta \simeq \frac{x/2}{2}\Rightarrow \frac{\lambda }{9}\simeq \frac{x}{4} $ $ x\simeq \frac{4\lambda }{a}\simeq \frac{4\times 600\times {10^{-9}}}{{10^{-3}}}m $ $ \simeq 24\times {10^{-4}}m $ $ \simeq 2.4\times {10^{-3}}m $ $ \simeq 2.4mm $
