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

Two thin lenses of powers +10 D and −4 D are placed in contact. The net power of the combination is:

Answer: 6 D.

A −6 D
B 4 D
C 6 D
D 14 D

Correct answer: C. 6 D

Explanation: Powers add in contact: P = 10 + (−4) = 6 D.

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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Two thin lenses of powers +10 D and −4 D are placed in contact. The net power of the combination is:

Concept context

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