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Questions
Write two important advantages of reflecting telescope over a refracting telescope.
Explain two advantages of a reflecting telescope over a refracting telescope
State any one advantage ·of using a reflecting telescope in place of a refracting telescope.
Solution 1
The two advantages of a reflecting telescope over a refracting telescope are as follows:
(i) There is no chromatic aberration in case of reflecting telescopes as the objective is a mirror.
(ii) Spherical aberration is reduced in case of reflecting telescopes by using mirror objective in the form of a paraboloid.
Solution 2
Two advantages of a reflecting telescope over a refracting telescope are:
1) Chromatic aberration is absent in reflecting type telescope whereas it is present in refracting type telescope. The absence of chromatic aberration in reflecting type telescope is because the objective is a mirror.
2) Images are brighter compared to that in a refracting type telescope.
Solution 3
Reflecting telescope remove chrometic and spherical aberration.
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RELATED QUESTIONS
Draw a labeled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power.
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| A number of optical devices and instruments have been designed and developed such as periscope, binoculars, microscopes and telescopes utilising the reflecting and refracting properties of mirrors, lenses and prisms. Most of them are in common use. Our knowledge about the formation of images by the mirrors and lenses is the basic requirement for understanding the working of these devices. |
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OR
Write two distinct advantages of a reflecting type telescope over a refracting type telescope.
With the help of a ray diagram explain the working of a reflecting telescope.
Draw a labelled ray diagram showing the image formation by a refracting telescope. Define its magnifying power.
Read the passage given below and answer the question that follows.
| There are two types of optical instruments: Microscopes and Telescopes. Microscopes are used to magnify very tiny objects whereas telescopes are used to study distant objects. Both of them deploy convex lenses. In his telescope, Newton used a large parabolic mirror to collect light from the stars and reduce aberrations. |
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-
What is the difference between a compound microscope and an astronomical telescope (refracting type), as far as their lenses are concerned?
Useful Constants & Relations:
| 1 | Charge of a proton | e | 1.6 × 10-19 C |
| 2 | Speed of light in vacuum | c | 3 × 108 ms-1 |
| 1 u = 931 MeV | |||
Assertion: An astronomical telescope has an objective lens having large focal length.
Reason: Magnifying power of an astronomical telescope varies directly with focal length of the objective lens.
