Question

how will you investigate the existance of the radiation beyond the red and violet extremes of the spectrum

Answer 1

Ultraviolet radiations are present at a violet extreme of the spectrum. It is detected when Ultraviolet radiations are passed through silver chloride solution. First of all, violet color appears then turn into dark brown color.  

Infrared radiations are present at a red extreme of the spectrum. If these radiations are placed around a blackened bulb thermometer.  It shows several readings on it.
 
Hope this will help you.

Answer 2

Explanation:

• Beyond the red light of the spectrum is ultra violet ray which can be investigated as it causes fluorescence on striking fluorescent material and affect photographic plate and beyond violet extreme there is infrared waves which can be investigated as its heating effect is more and mercury level Rises rapidly when thermometer with black bulb is kept in this radiation.