Question

In telescopes for a given wavelength, the objectives with large aperture are used for

• A. greater resolution.
• B. reducing lens aberration.
• C. greater magnification.
• D. ease of manufacture.

Hint:

Resolving power of a telescope is \(\dfrac{D}{1.22\lambda}\), so it grows with aperture \(D\).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
The limit of resolution of a telescope objective of aperture \(D\) is \(\Delta\theta=\dfrac{1.22\lambda}{D}\).

Step 2: Detailed Explanation
A larger aperture means a smaller \(\Delta\theta\) for the same wavelength, so two close stars can be separated. This is greater resolution.
A bigger lens also gathers more light, but the question asks for the reason given for a fixed wavelength, which is resolution.

Final Answer:
Large apertures give greater resolution, option (A). \[ \boxed{\text{Greater resolution (A)}} \]