Question

(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` ?

Answer 1

(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 refractine telescope.
(iv) Mirror requires griding and polishing of only one side.
(v) High resolution is resolution is achieved by using a mirror of large aperture (b) Here, `R = 80 cm`.
`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`