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Question
A point light source is kept in front of a convex mirror at a distance of 40 cm. The focal length of the mirror is 40 cm. Find the position of image.
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Solution
Given,
u = 40 cm (negative)
f = 40 cm (positive)
Mirror formula:
`1/u + 1/v = 1/f`
Substituting the values in the formula above, we get,
`- 1/40 + 1/v = 1/40`
`1/v = 1/40 + 1/40`
`1/v = (1 + 1)/40`
`1/v = 2/40`
`1/v = 1/20`
⇒ v = 20 cm.
The image is behind the mirror at a distance 20 cm.
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