Optics Question 1141
Question: The two slits at a distance of 1 mm are illuminated by the light of wavelength $ 6.5\times {{10}^{-7}}m $ . The interference fringes are observed on a screen placed at a distance of 1m. The distance between third dark fringe and fifth bright fringe will be
[NCERT 1982; MP PET 1995; BVP 2003]
Options:
A) 0.65 mm
B) 1.63 mm
C) 3.25 mm
D) 4.88 mm
Show Answer
Answer:
Correct Answer: B
Solution:
Distance between $ n^{th} $ Bright fringe and $ m^{th} $ dark fringe $ (n>m) $
$ \Delta x=( n-m+\frac{1}{2} )\beta =( 5-3+\frac{1}{2} )\times \frac{6.5\times {{10}^{-7}}\times 1}{1\times {{10}^{-3}}} $ = $ 1.63mm $
