Solved: PHYSICS Question for NEET

NEET PHYSICSEasy

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

a large aperture contributes to the quality and visibility of the images.

a large area of the objective ensures better light-gathering power.

a large aperture provides a better resolution.

all of the above.

Light Gathering Power: The objective lens needs to collect light from distant, often faint, objects. The light-gathering power is directly proportional to the area of the objective lens ( $Area \propto \text{Aperture}^2$ ). A larger aperture ensures a brighter image, improving visibility.
Resolving Power: The ability of a telescope to distinguish distinct details is called its resolving power, given by the formula $RP = \frac{D}{1.22\lambda}$ , where $D$ is the aperture (diameter) of the objective. A larger aperture ( $D$ ) results in higher resolution.
Image Quality: Since a large aperture improves both brightness (visibility) and resolution, it directly contributes to the overall quality of the image.
Focal Length: A large focal length ( $f_o$ ) is required for high magnifying power, as magnification $m = f_o/f_e$ . Thus, large focal length and large aperture are ideal characteristics.

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