Angular Magnification in Telescope

Q.

The magnifying power of a telescope with a tube length of $60cm$ is $5$. What is the focal length of its eyepiece?

1. $10cm$

2. $20cm$

3. $30cm$

4. $40cm$

Q. If the tube length of astronomical telescope is 105 cm long and magnifying power is 20 for normal setting. Calculate the focal length of objective.

1. 100 cm
2. 10 cm
3. 20 cm
4. 25 cm

Q. The eyepiece of a refracting telescope has $f=9\text{cm}$. In the normal setting, seperation between objective and eyepiece is $1.8\text{m}$. Find the magnification.

1. $20$
2. $19$
3. $18$
4. $21$

Q. For astronomical telescope
i) focal length of its objective should be larger than that of eyepiece
ii) focal length of its eyepiece should be larger than that of objective
iii) aperture of objective should be wider than that of eye piece
iv) aperture of the objective should be less wider than that of eye piece

1. i, ii. iii are true
2. ii, iii, iv are ture
3. ii, iii, and iv are true
4. i and iii are true

Q. The focal lengths of the lenses of an astronomical telescope are 50 cm and 5 cm. The length of the telescope when the image is formed at the least distance of distinct vision is

1. 45 cm
2. 55 cm
3. $\frac{275}{6}cm$
4. $\frac{325}{6}cm$

Q. The focal lengths of the objective and eye-piece of a telescope are respectively $100cm$ and $2cm$. The moon subtends an angle of ${0.5}^{\circ }$ at the eye. If it is looked through the telescope, the angle subtended by the moon’s image will be

1. ${100}^{\circ }$
2. ${50}^{\circ }$
3. ${25}^{\circ }$
4. ${10}^{\circ }$

Q. The magnifying power of an astronomical telescope is 8 and the distance between the two lenses is 54 cm. The focal length of eye lens and objective lens will be respectively

1. 6 cm and 48 cm
2. 48 cm and 6 cm
3. 8 cm and 64 cm
4. 64 cm and 8 cm

Q. If an object subtend angle of $2^{\circ }$ at eye when seen through telescope having objective and eyepiece of focal length $f_0=60cm$ and $f_e=5cm$ respectively then angle subtend by image at eye piece will be

1. ${16}^{\circ }$
2. ${50}^{\circ }$
3. ${24}^{\circ }$
4. ${10}^{\circ }$

Q. An astronomical telescope is to be designed to have a magnifying power of $50$ in normal adjustment. If the length of the tube is $102cm$, find the powers of the objective and the eyepiece.

1. $10;100$
2. $1;50$
3. $10;500$
4. $2;100$

Q. A telescope has objective and eye-piece of focal lengths 200 cm and 2 cm respectively. The magnifying power of the telescope for normal vision is

1. 90
2. 100
3. 108
4. 198

Q. Why don't we have a simple telescope?

1. We have simple telescope of short range.
2. We would need a convex lens of very huge focal length.
3. We would need a convex lens of very small focal length.
4. Simple telescope take a lot of time to make.
5. None of the above

Q. The diameter of the moon is $3.5\times {10}^{3}km$ and its distance from the earth is $3.8\times {10}^{5}km$. If it is seen through a telescope whose focal length for objective and eye lens are 4 m and 10 cm respectively, then the angle subtended by the image of the moon on the eye will be approximately

1. ${15}^{\circ }$
2. ${20}^{\circ }$
3. ${30}^{\circ }$
4. ${35}^{\circ }$