If the diameter of the objective of a telescope is increased, its resolving power:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Increases
The resolving power of a telescope is the reciprocal of the smallest angular separation it can resolve. Because of diffraction at the objective of diameter \( D \), this limiting angle is
\( \displaystyle \Delta\theta = \frac{1.22\,\lambda}{D} \)
\( \displaystyle \text{Resolving power} = \frac{1}{\Delta\theta} = \frac{D}{1.22\,\lambda} \)
The resolving power is directly proportional to the diameter of the objective. So increasing the diameter increases the resolving power; it stays finite for any finite diameter.
NCERT (2026-27):
Telescope – “… The resolving power, or the ability to observe two objects distinctly, which are in very nearly the same direction, also depends on the diameter of the objective. So, the desirable aim in optical telescopes is to make them with objective of large diameter.”