Question:

To increase magnifying power of telescope, we should increase:

Updated On: Aug 15, 2022
  • the focal length of the objective
  • the focal length of the eyepiece
  • aperture of the objective
  • aperture of the eyepiece
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The Correct Option is A

Solution and Explanation

Magnifying power of a telescope is $M=\frac{\text { angle subtended by final image at eye }}{\text { angle subtended by the object at eye }}$ When final image is formed at infinity, and $f_{o}$ is focal length of objective, $f_{e}$ is focal length of eye-piece then magnifying power is given by $M=\frac{f_{o}}{f_{e}}$ Since, $M \propto f_{o}$, therefore by increasing focal length of objective we can increase magnifying power.
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Concepts Used:

Ray Optics and Optical Instruments

Optics, deals with the determination of behaviour and the properties of light, along with its interactions with the matter and also with the instruments that are used to detect it.

Ray optics is also known as the geometrical optics and it is a branch of science which describes light propagation.

Reflection is the change in direction of light at an interface in-between two different media so that the wave-front returns into a medium from which it was originated.

Speed of light is the rate at which the light travels in free space.

A phenomenal change in image formed when the light is passed from one medium to another which is called Refraction.

Total Internal Reflection is the reflection of light when the light ray enters into a rarer medium from a denser medium and the angle of incidence is higher than the critical angle of incidence then that light ray will be reflected back to the denser medium.

Read More: Ray Optics and Optical Instruments