Focal length of a convex lens is $20 c m$ . Its power is

$+ 5 D$

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$+ 0.05 D$

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$- 0.05 D$

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Solution

The correct option is A
$+ 5 D$

Step 1: Given data
Lens is a convex lens.
Focal length, $f = + 20 c m = + 0.20 m$
Step 2: Formula used and calculation
Power of a lens is the inverse of its focal length (in metres).
Mathematically, $P = \frac{1}{f}$
$P = \frac{1}{f} P = \frac{1}{+ 0.20 m} P = + 5 D$
Hence, option (a) is correct.

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Focal length of a convex lens is 20cm. Its power is

The correct option is A +5DStep 1: Given dataLens is a convex lens.Focal length, f=+20cm=+0.20mStep 2: Formula used and calculationPower of a lens is the inverse of its focal length (in metres).Mathematically, P=1fP=1fP=1+0.20mP=+5DHence, option (a) is correct.

Focal length of a convex lens is $20 c m$ . Its power is