Optics Question 1159
Question: Two slits are separated by a distance of 0.5 mm and illuminated with light of $ \lambda =6000 $ Å. If the screen is placed 2.5 m from the slits. The distance of the third bright image from the centre will be
[CPMT 2005]
Options:
A) 1.5 mm
B) 3 mm
C) 6 mm
D) 9 mm
Show Answer
Answer:
Correct Answer: D
Solution:
Distance of the nth bright fringe from the centre $ x _{n}=\frac{n\lambda D}{d} $
Therefore $ x _{3}=\frac{3\times 6000\times {{10}^{-10}}\times 2.5}{0.5\times {{10}^{-3}}}=9\times {{10}^{-3}}m=9mm. $
