Is White light the only light that can be seperated into its constituent colours ? If not which other light can be seperated and how ? Also is there any other way of seperating white light into its constituents other than using a glass prism ?

 

No. White light is not the only light that can be separated into its constituent colours.

 

Any polychromatic light can be separated like that.

 

Example: Sodium light is composed of two yellow lines. It appears yellow and so one gets a feeling that it is monochromatic. 

When you take a sodium vapour lamp and focus its light on a prism and watch the refracted beam with a spectrometer, then you can observe the two components.

 

For splitting light into its constituent colours you need a material of greater refractive index than air. So, any material like water, oil, etc will solve the purpose.

However, using these materials is not feasible for experimental analysis and also they create large errors. So, a prism is the best device that can be used.