Question

An object 20cm from a spherical mirror give rise to a virtual image 15cm behind the mirror. The type of the mirror and
its focal length is
a)concave, 8.5cm
b)convex, 30cm
c)concave, 60cm
d)convex, 60cm
plss say the answer fasttt don't give wrong answers​

Answer 1

u = -20cm

v = +15cm

Formula Used:

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

Solution:

On substituting the values in the formula , we get:-

1/f = 1/15 - 1/20

1/f = 4 -3/60

1/f = 1/60 cm

f = +60 cm

Clearly the mirror will be convex mirror as the focal length is +ve.

therefore the answer will be

d) Convex mirror , +60 cm

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