What happens to the brightness of a ray of white light as it passes through a prism?
Each white ray contain the continuance spectrum with its profile. After it is passed through prism the result is a spectrum from red to violet. This spectrum has a curve, intensity against wave length which is same to white ray profile.
Yes, modified by the (wavelength dependent) absorption/scattering in the glass.
Yes. good point. Glass absorption also has influence to result, in here it's negligible because in visible region glass have no important absorption.
True enough, the OP did indicate they were talking about white light.
Separate names with a comma.