Calculate dispersive power of a transparent material given by:
n_v = 1.56, n_r = 1.54, n_y= 1.55

Given that,

n_v = 1.56, n_r = 1.54, n_y= 1.55
Dispersive power () = 

                            

(i) Spectrometer is used to observe spectrum.

(ii) 1. Function of Collimator : To render the rays parallel. 

2. Telescope : To observe the distant objects.