The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having greatest power is :
(a) P
(b) Q
(c) R
(d) S

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Solution

(c) R

Power = $\frac{1}{Focal length}$

Therefore, a lens with a small focal length will have more power.

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The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having greatest power is : (a) P (b) Q (c) R (d) S

(c) R Power = 1Focal length Therefore, a lens with a small focal length will have more power.

The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having greatest power is :
(a) P
(b) Q
(c) R
(d) S

(c) R

Power = $\frac{1}{Focal length}$

Therefore, a lens with a small focal length will have more power.