Question

An object of height 1.2 metre is placed before a concave mirror of focal length 20cm so that a real image is formed at a distance of 60 cm from it find the position of an object what will be the height of the image formed

Answer 1

the image is at infinity n is invisible

Answer 2

Hey mate.
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For a concave mirror:--
- - - - - - - - - - - - - -

Height of the object, h = 1.2m

Focal length of a concave mirror, f = - 20cm

Height of the image, h' = ?

Image Distance, v = - 60cm

Object Distance, u = ?

We know,

Mirror Formula :-
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$\frac{1}{f} = \frac{1}{v} + \frac{1}{u} \\ \\ = > \frac{1}{f} - \frac{1}{v} = \frac{1}{u} \\ \\ = > \frac{1}{( - 20) } - \frac{1}{( - 60)} = \frac{1}{u} \\ \\ = > \frac{ - 1}{20} + \frac{1}{60 } = \frac{1}{u} \\ \\ = > \frac{ - 1}{30} = \frac{1}{u} \\ \\ = > u = - 30cm$

Now,

Magnification = $\frac{ - v}{u}$

Thus,

h' /h = -v/u ( For concave mirror)

=> (-60/30) = (1.2)(-2)

= -2.4m.

The negative sign indicates inverted image.

Hope it helps ©