Question

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$<i>$◼Write the factors on which the focal length of a lens depends on?

◼Explain their dependence?

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⚫Invalid or incomplete answers will be reported!
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Answer 1

HEY MATE______________________________


There are three factors affecting the focal length of a lens.

1. refractive index of the material of lens.

2. refractive index of the surrounding medium

3. the radius of curvature of the lens surfaces.

HOPE THIS HELP YOU..

Answer 2

Answer:

The focal length depends on :-

➡ The refractive index of the surrounding medium .

➡ The radius of curvature of the lens .

Explanation:

The focal length is inversely proportional to the radius of curvature .

▶ If the radius of curvature is increased , then the lens becomes more thick . Hence the lens converges / diverges more thereby reducing the focal length.

▶ If the radius of curvature is decreased , then the focal length of the lens increases .

The focal length is directly proportional to the refractive index of the surrounding medium .

▶ Imagine that you kept the lens in water .

▶ There will be less refraction and hence the focal length is more .

▶ Now keep the lens in air which has less refractive index .

▶ The refraction will be more this time and thus the focal length will be less .

▶ So the refractive index of surrounding medium has a direct impact on focal length .