Target Exam

CUET

Subject

Physics

Chapter

Ray Optics

Question:

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.

Options:

20 cm, 1

1000 cm, 1

1010 cm, 1

1010 cm, 100

Correct Answer:

1010 cm, 100

Explanation:

The correct answer is Option (4) → 1010 cm, 100

Objective focal length, $f_0=10m=100cm×10=1000cm$

Eyepiece focal length, $f_e=10cm$

Tube length, $L = f_0 + f_e$

$=1000+10=1010 cm$

Angular Magnification, $M=\frac{f_0}{f_e} = \frac{1000}{10} = 100$