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.

Doubtly Asked 30 Oct 2026 NEET UG 2021 Practice test neet Save WhatsApp Report

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Answer: 4. all of the above.

Key idea: for a telescope objective, large focal length gives larger magnification, and large aperture helps three things.

A large aperture collects more light, so images are brighter and more visible.
Resolving power \(\propto D/\lambda\), so a large aperture also resolves finer detail.
Together this improves image quality.

All three statements are true, so option 4.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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