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प्रश्न
Read the following paragraph and answer the questions.
| 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. |
- Why the image formed at infinity is often considered most suitable for viewing. Explain
- In modern microscopes, multicomponent lenses are used for both the objective and the eyepiece. Why?
- Write two points of difference between a compound microscope and an astronomical telescope
OR
Write two distinct advantages of a reflecting type telescope over a refracting type telescope.
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उत्तर
- When the image is formed at infinity, we can see it with minimum strain in the ciliary muscles of the eye.
- The multi-component lenses are used for both the objective and the eyepiece to improve image quality by minimising various optical aberrations in lenses.
- (a)The compound microscope is used to observe minute nearby objects whereas the telescope is used to observe distant objects.
(b) In a compound microscope the focal length of the objective is lesser than that of the eyepiece whereas in a telescope the focal length of the objective is larger than that of the eyepiece.
OR
(a) The image formed by a reflecting type telescope is brighter than that formed by refracting telescope.
(b) The image formed by the reflecting type telescope is more magnified than that formed by the refracting type telescope.
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संबंधित प्रश्न
Draw a schematic ray diagram of a reflecting telescope showing how rays coming from a distant object are received at the eyepiece.
Draw a labeled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power.
With regard to an astronomical telescope of refracting type~ state how you will increase its:
1) magnifying power
2) resolving power
Draw a ray diagram showing the image formation of a distant object by a refracting telescope ?
Write the two important factors considered to increase the magnifying power?
Describe briefly the two main limitations and explain how far these can be minimized in a reflecting telescope ?
Draw a labelled ray diagram of an astronomical telescope to show the image formation of a distant object. Write the main considerations required in selecting the objective and eyepiece lenses in order to have large magnifying power and high resolution of the telescope.
(i) What is meant by resolving power of a telescope?
(ii) State any one method of increasing the resolving power of an astronomical telescope.
A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. Find the magnifying power of the telescope for viewing distant objects when
- the telescope is in normal adjustment,
- the final image is formed at the least distance of distinct vision.
Draw a ray diagram of Astronomical Telescope for the final image formed at infinity
