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

An astronomical telescope in normal adjustment has an objective of focal length 100 cm and an eyepiece of focal length 5 cm. Its magnifying power is:

Answer: 20.

A 500
B 20
C 105
D 95

Correct answer: B. 20

Explanation: In normal adjustment magnifying power M = f<sub>o</sub>/f<sub>e</sub> = 100/5 = 20.

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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An astronomical telescope in normal adjustment has an objective of focal length 100 cm and an eyepiece of focal length 5 cm. Its magnifying power is:

Concept context

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