Question

When an object is placed at a distance of 15 cm from a convex lens,
a real image is formed at a distance of 30 cm. What is the focal
length of the lens?​

Answer 1

Answer:

Explanation:

Solution,

Here, we have,

Image distance, u = - 15 cm

Object distance, v = 30 cm

To Find,

Focal length, f = ??

According to lens formula,

here we have,

1/f = 1/v - 1/u

Putting the value, we get

1/f = 1/v - 1/u

⇒ 1/f = 1/30 - 1/- 15

⇒ 1/f = 30 + 15/450

⇒ 1/f = 45/450

⇒ 1/f = 10 cm

Hence, the focal length is 10 cm.