Question Paper from: JEE Main 2021 - Paper 1

An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification '6', gives an unresolved image. A resolved image is observed at an infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0.6 m if the focal length of the eyepiece is equal to _______cm.

Correct Answer :

Solution:

Chapter Name: Optics

Difficulty Level: Moderate

magnification of microscopic lens

$m = 1 + \frac{D}{f _{0}}; 6 = 1 + \frac{25}{f _{0}}; f_{0} = 5 c m$

Magnification of compound microscope when image formed at infinity

$m = \frac{L}{f _{0}} \times \frac{D}{f _{e}}$

$12 = \frac{60}{5} \times \frac{25}{f _{e}}; f_{e} = 25 c m$

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