Question

How are power and focal length related ? You are provided with two lenses of focal length 20cm and 40cm respectively. Which lens will you use to obtain more convergent light?

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Answer 1

Explanation:

P=

f

1

To get more convergent one should use lens with high power since Power of a lens is inversely proportional to its focal length. Therefore lens having less focal length will provide more convergence.

one should use lens with 20cm focal length to get better convergence.

will provide more convergence.

Answer 2

$\sf \: p = \dfrac{1}{f}$

$\sf \: p \times \dfrac{1}{f} \: power \: of \: lens \: is \: inversely.$

Proportional to its focal length therefore having focal length of 20 length is 20 cm will provide more convergence