A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since: (a) a large aperture contributes to the quality and visibility of the images. (b) a large area of the objective ensures better light gathering power. (c) a large aperture provides a better resolution. (d) All the above.

Answer: (d). Large aperture collects more light, so images are brighter and more visible. Light gathering power ∝ D² (area of objective). RP = D/1.22λ, so a large aperture gives better resolution. Large fo gives large magnification m = fo/fe. So the answer is (d) All the above.

A lens of large focal length and large aperture is best suited as an… | NEET 2021

Q24NEET 2021Easy

Optical Instruments & the Eye

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

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Answer: (d)

Large aperture collects more light, so images are brighter and more visible.
Light gathering power $\propto D^2$ (area of objective).
$RP = D/1.22\lambda$ , so a large aperture gives better resolution.
Large $f_o$ gives large magnification $m = f_o/f_e$ .
So the answer is (d) All the above.

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