Question

The focal length of a convex lens in water medium compared air medium is​

Answer 1

Answer:

Decreases

Power of a lens =

f

1

Where f is the focal length of the lens.

So, by lens maker formula

f

1

=(

μ

1

μ

2

−1)(

R

1

1

−

R

2

1

)

As lens is dipped in water, μ of the medium is increased from 1 to

3

4

(i.e. refractive index of water), so,

μ

1

μ

2

term decreases, so, (

μ

1

μ

2

−1) term decrease which leads to decrease of

f

1

. so, power (=

f

1

) decreases.

Answer 2

Explanation:

Power of a lens =

f

1

Where f is the focal length of the lens.

So, by lens maker formula

f

1

=(

μ

1

μ

2

−1)(

R

1

1

−

R

2

1

)

As lens is dipped in water, μ of the medium is increased from 1 to

3

4

(i.e. refractive index of water), so,

μ

1

μ

2

term decreases, so, (

μ

1

μ

2

−1) term decrease which leads to decrease of

f

1

. so, power (=

f

1

) decreases.