Tag: observing space: telescopes

Quizzes (9) Questions (139)

Questions Related to observing space: telescopes

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

A reflecting telescope utilises :

  1. a convex mirror

  2. a concave mirror

  3. a prism

  4. a plano-concave lens
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Unlike convex mirrors, concave mirrors show different image types depending on the distance between the object and the mirror. That is why a reflecting telescope utilizes a concave mirror. If you observe the design of a reflecting telescope, it uses the incoming rays to focus through a concave mirror to focus on the second mirror which in turn sends the rays to the eye-piece. So, the concave mirror is intrinsic to the design of a reflecting telescope.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

This question has Statement-1 and Statement-2. Of the four choices given after the Statements, choose the one that best describes the two Statements.
Statement 1 : Very large size telescopes are reflecting telescopes instead of refracting telescopes.
Statement 2 : It is easier to provide mechanical support to large size mirrors than large size lenses.

  1. Statement-1 is true and Statement-1 is false and statement-2 is true

  2. Statement-1 is false and Statement-2 is true

  3. Statements-1 and Statement-2 are true and Statement-2 is correct explanation for Statement-1

  4. Statements-1 and Statements-2 are true and Statement-2 is not the correct explanation for Statement-1
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Large telescopes are reflecting telescopes because mirrors are easier to support from the back, whereas lenses must be supported at the edges, which causes sagging in large sizes.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

In the spectrum of light from a star, the wavelength of a particular line is measured to be $4747 $, while the actual wavelength of the line is $4700 $. What is the relative velocity ?

  1. $2\times10^5 m/s$
  2. $3\times10^5 m/s$
  3. $3\times10^6 m/s$
  4. $4.5\times10^6 m/s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the Doppler effect formula for light, delta_lambda / lambda = v / c, where delta_lambda = 4747 - 4700 = 47. Assuming typical values or a misprint in the prompt numbers where delta_lambda is 47 and lambda is 4700, v = c * (delta_lambda / lambda) = (3 x 10^8) * (47 / 4700) = 3 x 10^6 m/s.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

Match the items given in A, B, C and D against their corresponding description given in 1, 2, 3, 4 and 5.
A. Astronomical telescope
B. Galilean Telescope
C. Simple Microscope
D. Compound Microscope

1. Contains one convex lens
2. Contains one concave lens
3. Contains a convex lens of large focal length in the objective and a convex lens of small focal length in the eye-piece
4. Contains a convex lens of small focal length in the objective and a convex lens of large focal length in the eye-piece
5. Contains a convex lens of large focal length in the objective and a concave lens of small focal length in the eye-piece. 

  1. $2\, \quad\, 3\, \quad\, 1\, \quad\, 5$
  2. $3\, \quad\, 2\, \quad\, 4\, \quad\, 1$
  3. $2\, \quad\, 5\, \quad\, 3\, \quad\, 4$
  4. $3\, \quad\, 5\, \quad\, 1\, \quad\, 4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A). Astronomical telescope - Contains a convex lens of large focal length in the objective and a convex lens of small focal length in the eye-piece

B.) Galilean Telescope - Contains a convex lens of large focal length in the objective and a concave lens of small focal length in the eye-piece
C). Simple Microscope - Contains one convex lens
D.) Compound Microscope - Contains a convex lens of small focal length in the objective and a convex lens of large focal length in the eye-piece
Thus,
A  -  3 , B  -  5 , C  -  1 and D  -  4 , hence Option D is correct.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

The sum of the focal lengths of the objective and an eyepiece, In case of an astronomical telescope is equal to : ( final image is at $\infty$)

  1. The length of the telescope

  2. Half the length of the telescope

  3. Double the length of the telescope

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

The astronomical telescope makes use of two positive lenses: the objective, which forms the image of a distant object at its focal length, and the eyepiece, which acts as a simple magnifier with which to view the image formed by the objective. Its length is equal to the sum of the focal lengths of the objective and eyepiece, and its angular magnification is -fo/fe , giving an inverted image.
Hence, the sum of the focal lengths of the objective and an eyepiece, In case of an astronomical telescope is equal to the length of the telescope.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

In which of the following instruments is the final image virtual?

  1. Projector

  2. Camera

  3. Microscope

  4. Telescope
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

The final image of the camera and projector is real because it is obtained or projected on a screen or a photographic film or a chip.

A simple microscope uses convex lens and the object is placed between the focus and the optical center, so that, an erect, virtual and enlarged image of the object is formed.

A telescope uses two co-axially placed convex lenses in such a way that the focus of objective lens is past the focus of the eye piece. The first lens or the objective lens produces a real and inverted image of the object to be observed and this real image formed acts as an object for the eye piece convex lens and is between the focus and the optical center, so that, an inverted, virtual and enlarged image of the object is formed.

Hence, the correct answers are OPTIONS C and D.  

Multiple choice the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

Choose the correct answer from the alternatives given.
Maxwell in his famouse questions of  eletromagnetism introduce the concept of:

  1. ac current

  2. displacement current

  3. impedance

  4. reatance
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Maxwell in his famous question's of electromagnetism introduce the concept of displacement current

$J=J _E+J _C\ \quad=\epsilon _0\cfrac{dE}{dT}+\cfrac{dP}{dT}$

Multiple choice the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

Which of the following has/have zero average value in a plane electromagnetic wave?

  1. Both magnetic and electric fields

  2. Electric fields only

  3. Magnetic field only

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Both electric and magnetic field have sinusoidal nature in a plane electromagnetic wave. As we know, the average value of a sinusoidal wave is zero, so both magnetic and electric fields have average values zero.

Multiple choice the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

Which of the following is not true for electromagnetic waves?

  1. They transport energy.

  2. They have momentum.

  3. They travel at different speeds in air depending on their frequency.

  4. They travel at different speeds in medium depending on their frequency.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electromagnetic wave have constant velocity in a particular medium and it is independant of frequency and it is equal to $V=\sqrt{\dfrac{1}{\mu _0 \epsilon _0}}=3 \times 10^8 \ m/s$ 

Option C