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Define Its Magnifying Power and Write the Expression for It? - Physics

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प्रश्न

Define its magnifying power and write the expression for it?

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उत्तर

Magnifying Power: The magnifying power is the ratio of the angle α subtended at the eye by the final image to the angle β which the object subtends at the lens or the eye.

`m≈ β/α h/f_e  . f_o/h = f_o/f_e`

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2012-2013 (March) All India Set 3

संबंधित प्रश्‍न

You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason

Lenses Power (D) Aperture (cm)
L1 3 8
L2 6 1
L3 10 1

Draw a ray diagram showing the image formation of a distant object by a refracting telescope ?


Define magnifying power of a telescope. Write its expression.


A Galilean telescope is 27 cm long when focussed to form an image at infinity. If the objective has a focal length of 30 cm, what is the focal length of the eyepiece?


A lady cannot see objects closer than 40 cm from the left eye and closer than 100 cm from the right eye. While on a mountaineering trip, she is lost from her team. She tries to make an astronomical telescope from her reading glasses to look for her teammates. (a) Which glass should she use as the eyepiece? (b) What magnification can she get with relaxed eye?


Draw a labelled ray diagram showing the formation of an image by a refracting telescope when the final image lies at infinity.


Draw a ray diagram of a refracting astronomical telescope when final image is formed at infinity. Also write the expression for its angular magnification (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.
  1. Rohit observed the launch of Chandrayan 3 with the help of an optical instrument. Name the instrument used by him.
  2. State any one advantage of a reflecting telescope over a refracting telescope.
  3. Which instrument is used to study the structure of a virus?
  4. What is the ability of an optical instrument to form enlarged images called?
  5. 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.


A small telescope has an objective of focal length 140 cm and an eye piece of focal length 5.0 cm. The magnifying power of telescope for viewing a distant object?


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