Question

A parallel beam of light is made to fall on a concave lens. An image appears to be formed at a distance of 7 .5 cm from the lens. What are the focal length and the radius of curvature of the lens?

→ Don't spam.
→ No irrelevant answers.
→ No meet links.
​

Answer 1

Explanation:

1/v + 1/u = 1/f

so v = distance of object form mirror = infinity(i)

u = distance of image from mirror = 7.5

f = focal length of mirror = f

1/i + 1/7.5 = 1/f

0 + 1/7.5 = 1/f

f = 7.5 cm

radius of curvature=2f =2 x7.5 = 15cm