A luminous object is placed at a distance of `30 cm` from the convex lens of focal length `20 cm`. On the other side of the lens, at what distance from the lens a convex mirror of radius of curvature `10 cm` be placed in order to have an upright image of the object coincident with it ?

Options

A. 12 cm
B. 30 cm
C. 50 cm
D. 60 cm

Answer

C

Explanation

Here, `u = OC = -30 cm, f = 20 cm`
`(1)/(v)=(1)/(f)+(1)/(u)=(1)/(20)-(1)/(30)=(1)/(60)`
`v = 60 cm`
To obtain upright image of `O` at `O` itself,
`v = OC_1 = x + 10`
` :. x = v - 10 = 60 - 10 = 50 cm`.
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