Question

An object 2.5 cm high is placed at a distance of 10 cm from a concave mirror of radius of curvature 30 cm The size of the image is(a) 9.2 cm
(b) 10.5 cm(c) 5.6 cm(d) 7.5 cm

Answer 1

Option A is correct = 9.2 cm

Answer 2

Answer: (d) 7.5cm

Explanation:

It is given that

The height of object =2.5 cm

Object distance= 10cm

Radius of curvature =30 cm

We can solve this question using the mirror equation

The mirror equation is given by

1/f = 1/v + 1/u

f=R/2

=30/2

=15

The focal length is 15 cm

The object is placed in between focus and pole.

Hence the image will be obtained behind the mirror.

We will use the sign convention to solve the problem

f will be negative.

And

u will be negative.

Using the mirror formula,

(-1/15) = 1/v + (-1/10)

-0. 06= 1/v+ (-0.1)

v=30cm

using magnifying power formula

M. P = image distance / object distance

= 30/ 10

= 3

Also

M. P = size of image /size of object

3= size of image / 2.5

Therefore, size of image is 3* 2.5 = 7.5 cm