A convex mirror of focal length 'f' forms an image that is 1/nth the size of the object.How far is the object from the mirror? A)f/n-1 B)(n-1)f C)(n-1/n)f D)nf-1.Please explain.

Asked by ABHI BANSAL | 6th Nov, 2010, 04:53: PM

Expert Answer:

Dear student
Given that Magnification m = -v/u
so n = -v/u
that is, v = -nu
In the mirror equation
1/f = 1/v + 1/u
substituting for v
we get
1/f = 1/u - 1/nu
1/f = (n-1)/nu
(n-1)f = nu
u = (n-1)f / n
so u = (1-1/n)f
so correct option is C.
We hope that clarifies your query

Answered by  | 7th Nov, 2010, 06:19: AM

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