CBSE Class 10 Science 2017 · Paper 31/2/C · Question 3

Light - Reflection and Refraction 1 mark Easy

The power of a lens is

+ 0.5

D. Write its focal length.

Answer

$f = + 2$ m (+200 cm): the focal length is positive, so the lens is convex.

Focal length

f = \frac{1}{P} = \frac{1}{+ 0.5 D} = + 2

m, that is

+ 200

cm. The positive sign shows that it is a convex (converging) lens.

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