Q.50. One of the slits in Young’s double slit experiment is covered with a transparent sheet of thickness 2.9×10−3 cm. The central fringe shifts to a position originally occupied by the th 25th bright fringe. If λ=5800 Ao, the refractive index of the sheet is
A. 1.65
B. 1.60
C. 1.55
D. 1.50
Answer :- D. 1.50
Explanation :-
As it is given that a transparent sheet of certain thickness is inserted, we use:
(\mu - 1) \times t = N \lambda 25 \lambda = (\mu - 1) t \mu - 1 = \frac{25 \lambda}{t}\therefore The refractive index of the sheet is:
\mu = \frac{25 \times 5800 \times 10^{-10}}{2.9 \times 10^{-5}} + 1 \mu = 1.50