Optics Question 775

Question: Refractive index of air is 1.0003. The correct thickness of air column which will have one more wavelength of yellow light $ ( 6000{AA} ) $ than in the same thickness in vacuum is

[RPMT 1995]

Options:

A) 2 mm

B) 2 cm

C) 2 m

D) 2 km

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Answer:

Correct Answer: A

Solution:

For vacuum $ t=n{\lambda _{o}} $ …..(i)

For air $ t=(n+1){\lambda _{a}} $ …..(ii)

From equation (i) and (ii) $ t=\frac{\lambda }{\mu -1}=\frac{6\times {{10}^{-7}}}{1.0003-1} $

$ ( \mu =\frac{{\lambda _{o}}}{{\lambda _{a}}} ) $

$ =2\times {{10}^{-3}}m $ = 2mm.



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