DISPERSION f Lat. disprsio, from tlis pergcre, to disperse). It was shown by Sir Isaac Newton that if a beam of sunlight entered a darkened room through a small round opening. A, and fell upon a prism of glass. I', the light on leaving the prism consisted of colored beams. each beam having a different direction, but merging into its neighbor:. Instead of the beam of light falling on the screen at It(' and making a bright round while spot. the rays after traversing the prism are divergent and produee the prismatie band seen at ITV, the violet rays being bent or refracted 1 he mo-t. The eolors thus observed form what is lied it ..,peet run'.
better arrangement is to have as the source of light :1 slit parallel to the edge of the prism, a plan also tried by Newton.) \Vhite light is thus dispersed into color-. The angle between the beams of any two colors is the 'dis persion' of those colors for the given conditions of material and shape of prism and of incidence. Dispersion is due to the fact that
et her•w at es id different wave•nundier, and hence elm racterized by different colors if they are visilde—ti:n el in a material medium. e.g.
glass, VeleeitieS, a therefore have different refraction. The tells persion-curve' of given sul,ta nee is a drawn on hiving waeed•ngth and index or refraction as abscissa, showing how these quantities are for the substance. Itispersion may also be caused Va•ious interference and diff•actimi phenomena. Further, since dispersion is a characteristic of te a ve- mot ion. the a ssumpt ion being that some wave, travel faster than others in a given medium. it may be observed all kinds of N‘ a ves in suitable media. See Llemr.