⚛️ Physics · Ray Optics and Optical Instruments · NEET & JEE

In an achromatic doublet, two lenses of different materials are combined to eliminate chromatic aberration. Condition:

Answer: omega₁/f₁ + omega₂/f₂ = 0.

A f₁ = f₂
B omega₁/f₁ + omega₂/f₂ = 0
C omega₁ x f₁ = omega₂ x f₂
D omega₁ = omega₂

Correct answer: B. omega₁/f₁ + omega₂/f₂ = 0

Explanation: Achromatic doublet condition: omega₁/f₁ + omega₂/f₂ = 0, where omega is the dispersive power of each glass material.

Concave mirror ray diagram with an object drawn as a candle on the principal axis, the focal point F marked, and the parallel ray and focal ray reflecting to form an inverted real image

Concave mirror ray construction: a ray parallel to the axis reflects through F, and a ray through F reflects parallel, locating the inverted real image. Image: Maxmath12, CC0, via Wikimedia Commons.

Concept context

Reflection, refraction, lenses, mirrors, total internal reflection.

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In an achromatic doublet, two lenses of different materials are combined to eliminate chromatic aberration. Condition:

Concept context

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