Question

# A concave mirror has radius of curvature of 40cm. It is at the bottom of a glass that has water filled up to 5cm (see figure). If a small particle is floating on the surface of water, its image as seen, from directly above the glass, is at a distance d from the surface of water. The value of d is close to : (Refractive index of water =1.33)

A
8.8cm
B
11.7cm
C
6.7cm
D
13.4cm
Solution
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#### The correct option is A8.8cmLight incident from particle P will be reflected at mirroru=−5cm,f=−R2=−20cm1v+1u=1fv1=+203cmThis image will act as object for light getting refracted at water surfaceSo, object distance d=5+203=353cmbelow water surface,After refraction, final image is atd′=d(μ2μ1)=(353)(14/3)=354=8.75cm≈8.8cm

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