NEET Solved Paper 2018 Question 9
Question: In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength $ \lambda $ of the light used is $ 5896\overset{o}{\mathop{A}}, $ and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is $ 0\text{.20 }{}^\circ $ . To increase the fringe angular width to $ 0\text{.21 }{}^\circ $ (with same $ \lambda $ and D) the separation between the slits needs to be changed to [NEET - 2018]
Options:
A) 2.1 mm
B) 1.9 mm
C) 1.8 mm
D) 1.7 mm
Show Answer
Answer:
Correct Answer: B
Solution:
Angular width $ =\frac{\lambda }{d} $ $ 0.20{}^\circ =\frac{\lambda }{2mm} $ ..(i)
$ 0.21{}^\circ =\frac{\lambda }{d} $ ..(ii)
Dividing we get, $ \frac{0.20}{0.21}=\frac{d}{2mm} $
$ \therefore d=1.9mm $
