It is desired to make an achromatic combination of two lenses (L₁ and L₂) made of materials having dispersive powers $\omega_1$ and $\omega_2$ (< $\omega_1$ ). If the combination of lenses is converging then
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Question

It is desired to make an achromatic combination of two lenses (L₁ and L₂) made of materials having dispersive powers $\omega_1$ and $\omega_2$ (< $\omega_1$ ). If the combination of lenses is converging then

Options

G1 Physics · Accepted Answer

Derived solution: Step 1: For thin prisms/lenses use dispersion relations. For an achromatic doublet, ω₁P₁ + ω₂P₂ = 0, while the net power is P₁ + P₂. Step 2: Substitute the values given in the question and apply the geometry/sign convention shown. Step 3: On simplification the result is L₂ is converging. Therefore the correct option is B.

It is desired to make an achromatic combination of two lenses (L₁ and L₂) made of materials having dispersive powers ω 1 \omega_1 ω 1 ​ and ω 2 \omega_2 ω 2 ​ (&lt; ω 1 \omega_1 ω 1 ​ ). If the combination of lenses is converging then

It is desired to make an achromatic combination of two lenses (L₁ and L₂) made of materials having dispersive powers ω 1 \omega_1 ω 1 and ω 2 \omega_2 ω 2 (< ω 1 \omega_1 ω 1 ). If the combination of lenses is converging then