Question

With regard to an astronomical telescope for refracting type, state how you will increase its:
(i). Magnifying power.
(ii). Resolving power.

Answer 1

Use the formula for magnifying power and resolving power.

Formula used: $M=\dfrac{{{f}_{o}}}{{{f}_{e}}}$
Here
$M$ is the magnifying power
${{f}_{o}}$ is the focal length of the objective lens
${{f}_{e}}$ is the focal length of the eyepiece lens.
$\text{Resolving Power = }\dfrac{D}{1.22\lambda }$
Here
$D$ is the diameter of the objective lens
$\lambda$ is the wavelength of the incident light

Complete step by step solution:
An astronomical telescope for refracting type has an objective lens which gathers light from a source at infinity and focuses it in its focal plane. A diverging eyepiece lens intercepts them to form a clear, bright and magnified image.

(i). Magnifying power is the extent to which the object being viewed appears enlarged. The focal length of the objective lens should be large and the focal length of the eyepiece lens should be small to increase the magnifying power.

(ii). Resolving power is defined as the ability to distinguish between two close lines or points in an object. The aperture or diameter of the objective lens should be large to increase the resolving power.

Note: The greater the resolving power, the smaller is the limit of resolution or the minimum distance between two lines or points that just be distinguished.