Basic Maths and Units and DimensionsHard

Question

An object is placed in front of an equiconvex lens with refractive index 1.5 and radius of curvature 30cm. Surface which is away from object is polished. Find the distance of object from lens so that object and image concide :-

Options

A.10 cm
B.20 cm
C.15 cm
D.40 cm

Solution

    
f′ =
=
= 7.5 cm
Concave mirror
u = 2f′ = 2 × 7.5 = 15 cm

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