Physics, asked by mun49, 1 year ago

two lenses of focal length 20 cm and 40 cm are kept in contact with each other the power of equivalent length will be

Answers

Answered by GovindRavi
12
f1 = 20cm = 20 cm × 1 m / 100 = 1/5 meter
f2 = 40cm = 40 cm × 1m / 100 = 2 /5 meter

p1 = 1 / f1 = 1 / ( 1 / 5 ) = 5 D
p2 = 1 / f2 = 1 / ( 2 / 5 ) = 5 / 2 D = 2.5 D

equivalent power , p = p1 + p2 = 5 + 2.5 = 7.5 D
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