Optics Question 1081

Question: In a Young’s double slit experiment, the fringe width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3 without disturbing the geometrical arrangement, the new fringe width will be

[CBSE PMT 1990]

Options:

A) 0.30 mm

B) 0.40 mm

C) 0.53 mm

D) 450 micron

Show Answer

Answer:

Correct Answer: A

Solution:

$ \beta =\frac{\lambda D}{d};\ \ \therefore B\propto \lambda $

$ \frac{\lambda ‘}{\lambda }=\frac{0.4}{4/3}\Rightarrow \lambda ‘=0.3\ mm $ .



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