Physics, asked by mogillavamshi, 9 months ago

the refractive index of the material of a concave lens is 1.5 and radii of curvature are 40 cm and 60 cm respectively. find the focal length of the lens when it is kept in air

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Answered by Anonymous
24
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Answered by sonuvuce
0

The focal length of the mirror is 240 cm

Explanation:

Given:

The refractive index of concave lens \mu=1.5

The radius of curvature

R_1=40 cm

R_2=60 cm

To find out:

The focal length of the lens in air

Solution:

We know that the relation between the given quantities and focal length f is

Since the lens is concave, R_1 will be left facing hence negative and R_2 will be right facing hence positive

\frac{1}{f}=(\mu-1)(\frac{1}{R_1}-\frac{1}{R_2})

\implies \frac{1}{f}=(1.5-1)[\frac{1}{(-40)}-\frac{1}{(-60)}]

\implies \frac{1}{f}=(1.5-1)[-\frac{1}{40}+\frac{1}{60}]

\implies \frac{1}{f}=0.5\times(-\frac{1}{120})

\implies \frac{1}{f}=-\frac{1}{240}

\implies f=-240 cm

Hope this answer is helpful.

Know More:

Q: A double concave lens with the refractive index 1.5 is kept in the air . Its two spherical surfaces have radii R1 = 20 cm and R2 = 60 cm . Find the focal length of the lens . Write the characteristics of the lens.

Click Here: https://brainly.in/question/1135604

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