(a) List some advantanges of a reflecting telescope, especially for high resolution astronomy.
(b) A reflecting type telescope has a large mirror for its objective with radius of curvature equal to `80 cm`. What is the magnifying power of telescope if eye piece used has a focal length of `1.6 cm` ?

Explanation

(a) (i) There is no chromatic aberration as the objective is a mirror.
(ii) Spherical aberration is reduced using mirror objective in the form of a paraboloid.
(iii) Image is brighter compared to that in a refracting telescope.
(iv) Mirror requires grinding and polishing of only one side.
(v) High resolution is achieved by using a mirror of large aperture.
(b) Here, `R = 80 cm`
Focal length of objective mirror
`f_0 = ( R)/(2)=(80)/(2) = 40 cm`
and `f_e = 1.6 cm`.
As Magnifying power, `m = (f_0)/(f_e)`
`:. m = (40)/(1.6) = 25`.