why do the colours of wet objects appear richer and deeper than dry ones?

why is the prism spectrum more spread out at the violet end than the red end?

thanks

I've checked the answer for whether a spectrum is produced when a beam of light passes through a hollow prism....they've said there is no change of medium ...so there is no spectum produced. But, what about the change in medium from glass to air(inside the hollow prism) and then from air(inside the hollow prism) to glass....is there no spectrum produced?

thanks.

which are the rays having speed that of light

mention the functions of the following in spectroscope :-

A.) collimnator

B.) lens

C.)slit

D.)telescope

what is the difference between rayleigh scattering and raman scattering?