Question

Write three conditions necessary to obtain a pure spectrum on a screen. Name the instrument in which the conditions stated by you are fulfilled.

Answer 1

The three conditions necessary to obtain a pure spectrum on a screen are: 

(i) A narrow parallel beam of light should be made incident on the prism. 

(ii) The prism should be placed in the position of minimum deviation. 

(iii) The emergent parallel beam should be focussed on the screen. These conditions are fulfilled in spectrometer.