If the power of a lens is $+ 5$ dioptre, what is its focal length?

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Solution

Step 1 - Given data.
Power of the lens is, $P = + 5 D$
Step 2 - Finding the focal length.
The relation between the focal length and the power of the lens is given by, $P = \frac{1}{f}$ where $f$ is the focal length.
$+ 5 D = \frac{1}{f} f = 0.2 m (1 m = 100 c m) f = 20 c m$
Hence, the focal length of the lens is $+ 20 c m$ .

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If the power of a lens is +5 dioptre, what is its focal length?

Step 1 - Given data.Power of the lens is, P=+5DStep 2 - Finding the focal length.The relation between the focal length and the power of the lens is given by, P=1f where f is the focal length. +5D=1ff=0.2m1m=100cmf=20cmHence, the focal length of the lens is +20cm.

If the power of a lens is $+ 5$ dioptre, what is its focal length?