Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
- In normal adjustment:
Magnifying power (m) = `"f"_"o"/"f"_"e" = (140/5)` = 28 - When the final image is formed at the least distance of distinct vision (25 cm):
m = `"f"_"o"/"f"_"e" (1 +"f"_"e"/"D" ) = (28 xx 1.2) = 33.6`
APPEARS IN
संबंधित प्रश्न
- For the telescope is in normal adjustment (i.e., when the final image is at infinity)? what is the separation between the objective lens and the eyepiece?
- If this telescope is used to view a 100 m tall tower 3 km away, what is the height of the image of the tower formed by the objective lens?
- What is the height of the final image of the tower if it is formed at 25 cm?
Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.
With regard to an astronomical telescope of refracting type~ state how you will increase its:
1) magnifying power
2) resolving power
Write the two important factors considered to increase the magnifying power?
"A telescope resolves whereas a microscope magnifies." Justify this statement ?
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.
Define its magnifying power and write the expression for it?
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.
Draw a labelled ray diagram showing the image formation by a refracting telescope. Define its magnifying power.
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.
