A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope…

A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since:
  1. a large aperture contributes to the quality and visibility of the images.
  2. a large area of the objective ensures better light gathering power.
  3. a large aperture provides a better resolution.
  4. all of the above.

Solution

The formula of magnification power and resolving power of a telescope is, M.P. = f0fe & R.P.=a 1.22 λ. A large aperture(a) of the objective lens provides better resolution so, the good quality of the image is formed, and also it gathers more light. The larger the objective, the lighter the telescope collects and increases the brightness of the image and large focal length enhances the magnifying power of the telescope.

Asked in: NEET 2021

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