A thick plane-convex lens made of crown glass (refractive index 1.5) has thickness of 3 cm at its centre. The radius of curvature of the spherical surface is 5 cm.
An link mark made at the centre of its plane face, when viewed normal through the curved face, appears to be at a distance x from the curved face. Then, x is equal to
Given :
Radius of curvature, R=-5 cm
Object distance, u=-3 cm
The refractive indices n1=1.5 (glass), n2=1.0(air)
We have , 
(The Lensmaker’s formula)
v= -2.5 cm
Then the image will appear at distance of 2.5 cm from the plane surface of the mirror
Hence D is the correct option.
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