Question 3
Find the power of a concave lens of focal length 2 m.

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Solution

We know that, focal length is negative for concave lens.
Thus, focal length of the given concave lens, f = -2 m
$∴$ Power of lens,
$P = \frac{1}{f} = \frac{1}{(- 2)} = - 0.5 D$

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Q. Question 3
Find the power of a concave lens of focal length 2 m.

Question 8
Which of the following statements is true?
(a) A convex lens has 4 dioptre power having a focal length 0.25 m.
(b) A convex lens has -4 dioptre power having a focal length -0.25 m.
(c) A concave lens has 4 dioptre power having a focal length 0.25 m.
(d) A concave lens has 4 dioptre power having a focal length -0.25 m.

Find the power of a concave lens of focal length 2 m.

Q. Find the power (with sign) of a concave lens of focal length

20 c m

Q. The focal length of a concave lens is 2 m, calculate the power of the lens.

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Question 3 Find the power of a concave lens of focal length 2 m.

We know that, focal length is negative for concave lens. Thus, focal length of the given concave lens, f = -2 m ∴ Power of lens, P=1f=1(−2)=−0.5 D

Question 3
Find the power of a concave lens of focal length 2 m.

We know that, focal length is negative for concave lens.
Thus, focal length of the given concave lens, f = -2 m
$∴$ Power of lens,
$P = \frac{1}{f} = \frac{1}{(- 2)} = - 0.5 D$