KVPY SA Exam 2015 Question Paper

Question : 66 of 80

Marks: +1, -0

PHYSICS

A girl sees through a circular glass slab (refractive index 1.5) of thickness 20 mm and diameter 60 cm to the bottom of a swimming pool. Refractive index of water is 1.33. The bottom surface of the slab is in contact with the water surface.

The depth of swimming pool is 6 m. The area of bottom of swimming pool that can be seen through the slab is approximately

100 m $^{2 }$
160 m $^{2 }$
190 m $^{2 }$
220 m $^{2 }$

Validate

Solution:

Snell law

1 × \sin 90=4/3\sinr

\sinr=3/4

\tan r =3/√7

x = 6 \tan r ={6×3 }/√7=18/√7=6.8

(D) diameter

= 2x + 0.6 = ⇒ 14.2

Area =

{πD^2}/4={{3.14×(14.2)^2}/4\;\;m^2≈ 160m^2

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