Question:medium

For an astronomical telescope having objective lens of focal length 10 m and eyepiece lens of focal length 10 cm, telescope’s the tube length and magnification respectively are __________.
.Fill in the blank with the correct answer from the options given below.

Updated On: Mar 27, 2026
  • 20 cm, 1
  • 1000 cm, 1
  • 1010 cm, 1
  • 1010 cm, 100
Show Solution

The Correct Option is D

Solution and Explanation

An astronomical telescope comprises an objective lens and an eyepiece lens. The telescope's tube length is the sum of the focal lengths of these two lenses. Given:

Focal length of the objective lens, \( f_o = 10 \, \text{m} = 1000 \, \text{cm} \)

Focal length of the eyepiece lens, \( f_e = 10 \, \text{cm} \)

The tube length, \( L \), is calculated as:

\( L = f_o + f_e \)

Substituting the provided values:

\( L = 1000 \, \text{cm} + 10 \, \text{cm} = 1010 \, \text{cm} \)

The magnification \( M \) is determined using the formula:

\( M = \frac{f_o}{f_e} \)

With the given values:

\( M = \frac{1000 \, \text{cm}}{10 \, \text{cm}} = 100 \)

Consequently, the tube length measures 1010 cm, and the magnification is 100. The final answer is: 1010 cm, 100

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