Question

A biconvex lens of focal length f is cut into two identical plano convex lenses. Focal length of each part will be?​

Answer 1

Answer:

Explanation:

It will be 2f

Please mark me as a brain list

The explained solution is there in image have a look

Hope it will help u

Answer 2

Given: Focal length of biconvex lens = f

The biconvex lens is cut to form two plano-convex lenses.

To Find: The focal length of the plano-convex lenses

Solution:

Let the focal length of a plano-convex lens be f'

Since the given lens is biconvex, the radius of curvature of both the faces will be the same

R₁ = R₂ = R

The Lensmaker formula is given as:

$\frac{1}{f}$    = (u  -  1)    $\frac{1}{R1} - \frac{1}{R2}$, where f is the focal length, u is the refractive index, R₁ and R₂

The same lens is cut into two pieces so the refractive index will be the same.

u₁ = u₂ = u

$\frac{1}{f}$  = (u-1)($\frac{1}{R} +\frac{1}{R}$)

$\frac{1}{f}$  = (u-1)($\frac{2}{R}$)                                                             ...  1

For the plano convex lens, R₁ = R and R₂ = ∞

$\frac{1}{f'}$ = (u-1) ($\frac{1}{R}- 0$)                                                                                 1/∞ = 0

$\frac{1}{f'}$ = (u-1)($\frac{1}{R}$)                                                               .. 2

From equation 1 and 2

f'  = 2f

Therefore, the focal length of the plano-convex lens is twice the focal length of the biconvex lens.