Question

A student uses a lens of focal length 50cm and another of -
50cm What is the lens and its power used by each of them?​

Answer 1

Two kinds of lenses are used in the question. Let's find out the powers.

Explanation:

Given: Two lenses with focal lengths of +50 cm and -50 cm.

To find: Power of each of the lenses.

Formula to be used: P = $\frac{1}{f}$

Solution:

• The first student has a lens of positive focal length, so he is having a convex lens also known as a converging lens.
• The second student has a lens of negative focal length, so he is having a concave lens also known as a diverging lens.

Power of each:

Lens 1:

P = $\frac{1}{f}$

P = $\frac{1}{50}$

P = 0.02 D

Lens 2:

P = $\frac{1}{f}$

P = $\frac{1}{(-50)}$

P = -0.02 D

Final answer:

The power of lens 1 and lens 2 are 0.02 D and -0.02 D respectively.