Question

# An object is placed at f2 away from first focus of a convex lens where f is the focal length of the lens. Its image is formed at a distance 3f2 in a slab of refractive index 32, from the face of the slab facing the lens. Find the distance of this face of the slab from the second focus of the lens. A
f2
B
3f2
C
2f
D
f
Solution
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#### u=−3f2 ; f=+f1v−1u=1f1v−−23f=1fv=+3fimage is formed at a distance 3f2 from the face i.e, in air it is a distance dμ=3f232=f from the faceso the distance between second focus and the face is 3f−f−f=foption D is correct

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