Step 1: Understanding the Question:
Resolving power is the ability of an optical instrument to distinguish between two close objects. We need to identify which factor increases it for a telescope. Step 2: Key Formula or Approach:
The resolving power (RP) of a telescope is given by:
\[ \text{RP} = \frac{D}{1.22 \lambda} \]
where \(D\) is the diameter of the objective lens (aperture) and \(\lambda\) is the wavelength of light used. Step 3: Detailed Explanation:
From the formula:
1. \(\text{RP} \propto D\): Increasing the diameter of the objective lens increases the resolving power.
2. \(\text{RP} \propto \frac{1}{\lambda}\): Decreasing the wavelength of light increases the resolving power.
Looking at the options:
(A) Eyepiece diameter does not affect resolution.
(B) Increasing wavelength decreases RP.
(C) Eyepiece focal length affects magnification, not resolution.
(D) Increasing the diameter of the objective increases RP. Step 4: Final Answer:
Resolving power can be increased by increasing the diameter of the objective.