Question

A convex lens of focal length 4 CM is used in simple microscope then it's magnifying power when image at ddv is

Answer 1

Given:

A convex lens of focal length 4 cm is used in simple microscope.

To find:

Magnifying Power of the microscope ?

Calculation:

First of all , how is magnifying power defined?

• Magnifying power of a simple microscope is defined as the ratio of the angle subtended at the eye when seen through the lens to the angle subtended by the object at the unaided eye.

• Both are placed at near point of a normal eye.

For a simple microscope / magnifying lens:

Let magnifying power be M , f be focal length and d be the near point.

$\sf \therefore \: M = 1 + \dfrac{d}{f}$

$\sf \implies \: M = 1 + \dfrac{25}{4}$

$\sf \implies \: M = 1 + 6 .25$

$\sf \implies \: M = 7.25$

So, magnifying power is 7.25 .