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Physics

Power of a Lens

An achromatic...

Question

An achromatic convergent doublet of two lenses contact has a power of +2D. The convex lens has power +5D. What is the ratio of dispersive powers of convergent and divergent lenses?

2 : 5

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3 : 5

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5 : 2

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5 : 3

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Solution

The correct option is B 3 : 5
Goven: $P_{1} = 5 D$
$P - 2 = P - P_{1} = 2 - 5 = - 3 D$
$\frac{ω_{1}}{ω_{2}} = - \frac{f_{1}}{f_{2}} = \frac{- P_{2}}{P_{1}} = \frac{3}{5}$

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An achromatic convergent doublet of two lenses contact has a power of +2D. The convex lens has power +5D. What is the ratio of dispersive powers of convergent and divergent lenses?

The correct option is B 3 : 5Goven: P1=5DP−2=P−P1=2−5=−3Dω1ω2=−f1f2=−P2P1=35

The correct option is B 3 : 5
Goven: $P_{1} = 5 D$
$P - 2 = P - P_{1} = 2 - 5 = - 3 D$
$\frac{ω_{1}}{ω_{2}} = - \frac{f_{1}}{f_{2}} = \frac{- P_{2}}{P_{1}} = \frac{3}{5}$