Question

An object placed 20cm in freart of a mirror is found to have an image 15cm(a)in front of it (b)behind the mirror and the kind of mirror in each case.


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Answer 1

A. convex mirror

B. concave mirror

Answer 2

Answer:

CASE A

with sign convention

u= -20 v= -15

using mirror formula

1/v+1/u=1/f

-1/15-1/20 =1/f

-4-3/60=1/f

f= -60/7

since f is negative, therefore it is a concave mirror.

CASE B

U= -20 v= +15

using mirror formula

1/v+1/u= 1/ f

1/15-1/20=1/f

4-3/60=1/f

f=60

f is positive so it is a convex mirror.