Question

 A 3 cm tall object is placed 18 cm in front of a concave mirror of focal length 12 cm. At what distance from the mirror should a screen be placed to see a sharp image of the object on the screen. Also calculate the height of the image formed. 

Answer 1

Answer:

The image height will be 6cm.

Explanation:

We have,

u = -18

f = -12

We have to calculate

v = ???

Using the mirror equation

1/f = 1/v + 1/v

=> 1/v + (-1/18) = -1/12

=> 1/v = 1/12 + 1/18

=> 1/v = (-3+2)/36

=> 1/v = -1/36

=> v = -36cm

Magnification, m = -v/u

Also

m = height of image/height of object

m = -36/-18

m = 36/18

m = 2

Now,

=> 2 = height of image/3

=> height of image = 6cm

Therefore, the image height will be 6cm.