Question

An object of height 7cm is kept at a distance of 25cm in front of a concave mirror. The focal length of the mirror is 15cm. At what distance from the mirror should a screen be kept so as to get clear image? What will be the size and nature of the image?

Answer 1

Given that,

For concave mirror,

Object height h1= 7cm

Object distance u= -25cm

Focal length f= -15cm

We know that, the mirrors formula is given by,

1/f = 1/u + 1/v

1/-15= 1/-25 + 1/v

Thus, 1/v = -1/15 + 1/25

1/v = -2/75

Hence, v= -37.5cm

Thus, as the image will be formed at a distance 37.5cm from the concave mirror hence, screen should be kept at a distance 37.5cm from the concave mirror.

 

We know that, the magnification is given by,

m= h2/h1= -v/u

h2/7= 37.5/-25

Thus, h2= -10.5cm

Thus, the size of the image formed will be 10.5cm.

From the above data we can say that the image formed will be real and inverted.