Question

An object is placed at a distance of 5cm in front of a concave mirror of radiusof curvature 20cm. Find the magnification of the image formed?

Answer 1

.magnification is equal to 2
U'll be able to get it by seeing the image

Answer 2

Data:
Radius of curvature of concave mirror = r = 20 cm
The radius of curvature is twice the focal length. So,
r = 2f 
20 = 2 f
20/2 = f
f = 10 cm
Since image is formed on the same side of the mirror.So,
f = - 10 cm
Object distance = u = - 5 cm
Image distance = v = ?
Magnification = m = ?
Solution:
Using mirror formula:
1/v + 1/u = 1/f
1/v =  1/f - 1/u
1/v = - 1/10 + 1/5
1/v = 1/10
v = 10 cm
So, image is formed at 10 cm from the pole of the mirror.
Now.
Magnification = m = - v/u
Magnification = m = - 10/ -5
Magnification = m = 2 
This is the required answer.
Hopefully it helps. Thanks.