Question

Which of the following changes improves the resolving power of a telescope?

Options

• Increasing the focal length of the eyepiece only

• Decreasing the aperture of the objective

• Increasing the aperture of the objective

• Placing the final image at the least distance of distinct vision

Answer 1

Resolving power is the inverse of the angular separation given by $\sin\theta = 1.22\,\frac{\lambda}{d}$. Since a larger aperture $d$ makes $\theta$ smaller, a larger aperture gives better resolving power, allowing two closely spaced objects to be seen as distinct images.