Question

Which scientist first discovered that white light is a mixture of a rainbow spectrum of light rays?

Answer 1

possibly using a dispersive glass prism, the spectrum is often attributed to Newton. I think he may have written something (in Latin) called "Optiks" about it.

Answer 2

Newton understood that white light can be separated into its components because each ray of colour is deviated by the glass of the prism by a different amount. He realized, for example, that red light is consistently less deviated than violet light.