A concave lens has a focal length of 50 cm. Calculate its power.

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Solution

Since it is a concave lens, the focal length will be negative.
Thus, focal length, $f = - 50 c m = - 0.5 m$
Now, Power, $P = \frac{1}{f (i n m e t r e s)}$
$= \frac{1}{- 0.5} = - 2 D$
Thus, the power of the concave lens is -2 dioptres.

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A concave lens has a focal length of 50 cm. Calculate its power.

Since it is a concave lens, the focal length will be negative. Thus, focal length, f=−50 cm=−0.5 m Now, Power, P=1f(in metres) =1−0.5=−2 D Thus, the power of the concave lens is -2 dioptres.

Since it is a concave lens, the focal length will be negative.
Thus, focal length, $f = - 50 c m = - 0.5 m$
Now, Power, $P = \frac{1}{f (i n m e t r e s)}$
$= \frac{1}{- 0.5} = - 2 D$
Thus, the power of the concave lens is -2 dioptres.