Question

A 6 cm object when placed at a distance of 20 cm forms a
real image at 12cm . Calculate the focal length of the mirror,
magnification and height of the image .​

Answer 1

Answer:

This problem is missing info, but my guess is it is not a typo but intentional, and I think its intent is to make you think. The info that is missing is the nature of the image. We are not told if the image is REAL or VIRTUAL. By inspection, however, we can deduce that the image is real. Di < Do. The condition in convex mirrors providing virtual image is Di > Do.

If Di > Do, then there would have been two separate solutions.

In this case; 1/f = 1/20 + 1/12 → f = 7.5 cm