Question

What is meant by resolving power of a telescope?
State any one method of increasing the resolving power of an astronomical telescope.

Answer 1

In telescopes, very close objects such as binary stars or individual stars of galaxies subtend very small angles on the telescope. To resolve them we need very large apertures.The angular separation between two objects must be

$\Delta \theta =1.22\frac{\lambda }{d}$

resolving power $\Rightarrow \frac{1}{\Delta \theta }=\frac{d}{1.22\lambda }$

For better resolution

1. $\sin \theta$ must be large. To achieve this, the objective lens is kept as close to the specimen as possible.

2. High refractive index medium should be used.

3. Decreasing the wavelngth by using $X$-rays and $\gamma$ rays.