prism

(prizm) (Gr. πρίσμα]. A solid with a tri an Τ or polygonal cro -section. A triangular prism splits up a ray of light into its constituent colors, and turns or deflects light-rays toward its base. Prisms are used to correct deviations of the eyes, since they alter the apparent situation of objects. p.-diopter, the unit of prismatic refraction; a deflection of one centimeter at the distance of one meter. enamel-p. any one of the columns which make up the enamel of the teeth. Maddox p., two prisms with their bases to- ether: used in testing for torsion of the eyeball. icol p., two slabs of Iceland spar cemented together and deflecting a ray of light in such a way that it is split in two, one part being totally See milicria and The condition or Bearing or having A name of 718 PROBILIN reflected and the other (polarized ray) pa ing through. Risley’s p., a prism which rotates in a metal frame marked with a scale: used in testing ocular muscles for imbalance.