Telescope

Q.

The near point of hypermetropic eye is 75 cm from the eye. What is the power of the lens required to enable him to read a book held at 25 cm from the eye?

1. 3.8D

2. 3D

3. 2D

4. 2.66D

Q. Which of the following is true regarding a reflecting telescope?

1. A reflecting telescope uses only lenses to see distant objects clearly.
2. A reflecting telescope uses only mirrors to see distant objects clearly.
3. A reflecting telescope uses both mirros and lenses to see distant objects clearly.
4. A reflecting telescope uses neither mirrors nor lenses to see distant objects clearly.

Q.

The type of lens used in a simple microscope is

1. Binocular lens

2. Plano concave lens

3. Concave-convex lens

4. Convex lens

Q. What are the advantages of a reflecting telescope over a refracting telescope?

1. Mirrors can be made bigger than lenses in size.
2. No chromatic aberration.
3. In case parabolic mirror is used, then no spherical aberration.
4. Some light gets blocked inside the refracting telescope, but not reflecting telescope.

Q. The magnifying power of a microscope with an objective of 5 mm focal length is 400. The length of its tube is 20 cm. Then the focal length of the eye-piece is (consider that final image is formed at infinity)

1. 200 cm
2. 160 cm
3. 2.5 cm
4. 0.1 cm

Q.

Why does a concave lens make things look smaller?

Q.

The spherical aberration can be minimized by

1. reducing the aperture of the lens

2. using specially made meniscus lens

3. combination of lenses made of different glasses

4. all the above

Q.

What is the difference between physical optics and geometric optics?

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. Which of the following statements is/are correct about a concave lens when an object moves from a large distance towards the lens?

1. The image shifts from the focus towards the optical centre of the lens.
2. The image’s size gradually increases, but it always remains smaller than the object.
3. The image formed is always inverted.
4. The image formed can be obtained on the screen.

Q.

Negative power indicates that it is not a:

1. Concave lens

2. Convex lens

3. Combination of both the lenses

4. None of these

Q. Choose the correct statement/s with respect to the lenses of a Refracting telescope.

1. The objective lens has large diamater and larger focal length.
2. The objective lens has large diamater but smaller focal length.
3. The eyepiece has small diameter and smaller focal length.
4. The eyepiece has small diameter but larger focal length.

Q.

Which kind of mirrors are used in solar concentrators?

Q.

Give your opinion about the radius of curvature of a convex lens having different focal lengths $F_1$ and $F_2$ ? What would the lens called have an equal focal length?

Q.

Which of the below-given option is correct about an astronomical telescope?

1. The image produced by the telescope is inverted

2. Its objective is a concave lens

3. Telescopes consists of two diverging lenses

4. Its eyepiece is a convex lens with a greater focal length than the objective lens.

Q. The mirror used in telescope to collect light is called ___.

1. Refractor
2. Reflector
3. Inferometer
4. Spectrometer

Q.

In astronomical telescopes, a larger ________ mirror is used to collect light from objects like stars and planets.

Q. In a radio telescope, the shape of the mirror used is .

1. plane
2. concave
3. convex

Q.

The near point of a hypermetropic eye is 75 cm from the eye. What is the power of the lens required to read a book held at 25 cm from the eye?

1. 3D

2. 2D

3. 2.66D

4. 3.8D

Q.

With what speed should a galaxy move outward with respect to earth so that the Sodium-D line at wavelength 5890 Å is observed at 5896 Å?

1. 306 km/sec

2. 322 km/sec

3. 296 km/sec

4. 336 km/sec

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. 100
2. 108
3. 90
4. 198

Q.

Difference between convex and concave lenses?

Q. The focal lengths of objective and eye lens of an astronomical telescope are $100cm$ and $5cm$, respectively. Calculate the magnifying power and length of an astronomical telescope for relaxed eye.

Q. The magnifying power of a telescope is 9. When it is adjusted for parallel rays, the distance between the eye-piece and objective lens is 20 cm. Find the focal length of both the lenses.

Q.

Which one of the following is the use of concave lens?

1. Used in Optical Instruments

2. Used as a camera lens

3. Used in a projector

4. Used in telescopes

Q. A Galileo telescope has an objective of focal length $100$ cm & magnifying power $50$. The distance between the two lenses in normal adjustment will be?

1. $200$ cm
2. $98$ cm
3. $100$ cm
4. $150$ cm

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. The focal lengths of an objective lens and eyepiece are $192cm$ and $8cm$ respectively in a small telescope. Calculate its magnifying power and the separation between the two lenses.

Q. (a) What is least distance of distinct vision for a normal human eye?
(b) With the help of labelled diagram. give the principle and magnifying power of astronomical telescope when final image is formed at least distance of distinct vision.

Q.

Sir

I am Shaun job of class 10, I have a doubt regarding physics on the topic of optics,

This is the question Sir

Why do wet clothes appear darker than dry clothes?

Thank you so much for your time Sir

Shaun