Question

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 of the above

Answer 1

The correct option is D All of the above

With larger aperture of objective lens, the light gathering power in the telescope is high.

Also, the resolving power or the ability to observe two objects distinctly also depends on the diameter of the objective. Thus, an objective of large diameter is preferred.

Also, with large diameters fainter objects can be observed, Hence it also contributes to the better quality and visibility of images.

Since, all given options are correct, so right option is $\left(\text{D}\right)$.