An astronomical telescope operating in normal adjustment consists of an objective lens wit… — JAMB UTME

An astronomical telescope operating in normal adjustment consists of an objective lens with a focal length of $80\text{ cm}$ and an eyepiece with a focal length of $4\text{ cm}$ . What is the magnitude of the angular magnification produced by the telescope?

Answer: 20

Answer

The magnitude of the angular magnification produced by the telescope is 20.

The angular magnification

M

of an astronomical telescope in normal adjustment is defined as the ratio of the focal length of the objective lens

f_o

to the focal length of the eyepiece lens

f_e

, given by

M = \frac{f_o}{f_e}

. Substituting the given values

f_o = 80\text{ cm}

and

f_e = 4\text{ cm}

yields

M = \frac{80}{4} = 20

Step-by-Step Solution

Identify the given optical parameters and formula for angular magnification.

Objective focal length

f_o = 80\text{ cm}

, Eyepiece focal length

f_e = 4\text{ cm}

. Formula:

M = \frac{f_o}{f_e}

For an astronomical telescope in normal adjustment, the light rays emerge parallel, and the angular magnification is given by the ratio of the focal length of the objective lens to that of the eyepiece.

Calculate the angular magnification value.

M = \frac{80\text{ cm}}{4\text{ cm}} = 20

Dividing the focal length of the objective lens by the focal length of the eyepiece yields the dimensionless magnification ratio.

Key Concept

Angular Magnification of an Astronomical Telescope in Normal Adjustment

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