Question

A concave mirror of focal length 20cm form a real image at a distance of 40cm.Find the position of the Object.

Plz answer me guys ,it's urgent plzzz
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Answer 1

Explanation:

Image distance, v = -40cm

Focal length, f = -20cm

Object distance, u = ?

We know that,

1/u + 1/v = 1/f

=> 1/u = 1/f - 1/v

=> 1/u = 1/-20 - (1/-40)

=> 1/u = -1/20 + 1/40

=> 1/u = -2/40 + 1/40

=> 1/u = -1/40

=> u = -40 cm