Question

A parallel beam of light is made to fall on a concave mirror. An image is formed at a distance of 7.5 cm from the mirror. What is the focal length and the radius of curvature of the mirror?

Answer 1

We know that when the beam of light is parallel, the object distance is at infinity.

The object is kept at infinity. In such a case, the image is formed at focus.

Thus we can say that:

Focal length = 7.5 cm

• Radius = 2 × focal length

Radius of curvature = 15 cm

Answer 2

Answer:

When ray of light is parallel to principal axis and fall on mirror then the image will formed on the Focal length and vice versa.

So,

V = f = 7.5 cm

and

Radius of curvature = 2 × Focal length

ROC = 2 × 7.5 = 15 cm

Explanation:

hope the answer will help you