Question

You are provided with two lenses of focal length 20cm and 30cm , respectively ,these lenses can diverge the light . Which lens will you use ti obtain more divergent light ? Name these lens .

Answer 1

lens with 20 cm focal length will diverge the light greater.

Because its a concave lens, f will be negative thus the power [inverse of focal length] of the lens with -20cm f will be greater than that of f -30cm.

Answer 2

Answer:

The lens having focal length 20 cm will be more divergent.

Explanation:

Given that,

focal length of first lens $f_{1}=20 cm$

Focal length of second lens $f_{2}= 30\ cm$

These lenses can diverge the light. These lens are concave lenses.

The power of the lens is reciprocal of the focal length of the lens.

$P=\dfrac{1}{f}$

The power of first lens is

$P_{1}=\dfrac{100}{20}$

$P_{2}=5 D$

The power of second lens is

$P_{2}=\dfrac{100}{30}$

$P_{2}=3.33$

The power is more of first lens as compare to other.

Therefore, first lens will obtain more divergent light.

Hence, The lens having focal length 20 cm will be more divergent.