Question

a rod of length 10 cm lies along the principle axis of a concave mirror of f=10 cm in such a way that the end closer to the pole is 20 cm away from it. find the length of the image

Answer 1

I hope this answer is helpful for you

Answer 2

The object lies horizontally on the principal axis. So let the object be AB. B lies 20 cm away from the pole and A lies 10+20 = 30 cm away from the pole.

C = 2f = 2(10). Center of Curvature is 20 cm. So point B is at center of curvature and so the image formed will be 20 cm away from the mirror(in the left side). OR you can also verify this with mirror formula.

Image of Point A will be formed at = 1/v + 1/u = 1/f

1/v = 1/f - 1/u

1/v = 1/-10 -1/-30 = -2/20

v = -30/2 = -15.

So image of point A will be at 15 cm in left side of mirror. Now callculate the length of the image. It is equal to 20 - 15 = 5. Image distance of B - Image distance of A.