Question

A convex mirror has a focal length of 18 cm. The image of an object kept in front of the mirror is half the height of the object. What is the distance of the object from the mirror?

Answer 1

If f= 19cm and given that, h₁ = h /2

h₁ / h = ½ , then u = ?

Apply the magnification formula, h₁ / h = – (v/ u)

v= -u × h₁ / h = – u/2

To, this use the mirror formula, 1/f = 1/v + 1/u

That is 1/ 18 = – 2/ u + 1/ u

u=-18 cm.

So, the distance of the object from the mirror is 18cm.