Question

Power of the lens is -40 its focal length is ??
A) 4m
B) -40m
C)-0.25m
D) -25m

Answer 1

the focal length is -0.25m

Answer 2

The focal length of the lens is -0.025 m.

Explanation:

The relation between power and focal length of the lens is given by

$P=\frac{1}{f(m)}$

Here, P is the power of the lens and f is the focal length of the lens in meter (m).

Given, P = - 40 D.

Substitute the value of the power in above formula, we get

$-40D=\frac{1}{f}$

$f=\frac{1}{-40D}$

f = -0.025 m.

Thus, the focal length of the lens is -0.025 m.

#Learn More:

Topic: Power of the lens.

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