Question

a convex lens of focal length 0.2m made of glass is immersed in water. find the change in focal length of the lens​

Answer 1

the focal length of the lens when immersed in water is 78cm.

hope it will help you

Answer 2

The change in focal length of the lens​ is 0.58 m.

Explanation:

Given the focal length of the convex lens is, F = 0.2 m.

Take the refractive index of the glass,  $\mu_g=1.5$.

The refractive index of the water,  $\mu_w=1.33$.

Use the lens maker formula in air as

$\frac{1}{F}=(\mu_g-1)(\frac{1}{R_1} - \frac{1}{R_2})$

Here, R_1 and R_2 are the radius of curvatures.

substitute the values, we get

$\frac{1}{0.2m} =(1.5-1)\frac{1}{R_1} - \frac{1}{R_2})$

$10=\frac{1}{R_1} - \frac{1}{R_2}$

Now focal length when lens immersed in water,

$\frac{1}{f}=(\frac{\mu_g}{\mu_w}-1 )(\frac{1}{R_1} - \frac{1}{R_2})$

substitute the values, we get

$\frac{1}{f}=(\frac{1.5}{1.33} -1)\times10m$

f = 0.78 m.

Therefore change in focal length, = focal length in water- focal length in air.

= 0.78-0.2=0.58 m.

Thus, the change in focal length of the lens​ is 0.58 m.

#Learn More: lens maker`s formula.

https://brainly.in/question/8024277