OPTICS

the science which deals wit) the nature and proper tics of light. O all the phenomena connected with light none are more important than reflect i or and refraction, and to understand thes it must be borne in mind that rays of lich | travel from an object fo the eye, and tha’ Petes ae Sah is seen in the direction in which the ray: enter the eye; thus an image seen in: plane mirror appears opposite the objec and equi-distant to it from the reflect in; | surface, ight ten takes place wher a ray of t — from one mediun into another of different density, provide: the ray docs not striko the surface of th refracting medium at right angles. 4 close ees ere of refraction has le to remarkable perfection in the construc | tion of lenses for spectacles, telescopes microscopes, etc., and to this phenomenon through the agency of the spectroscope is due the krowledge we have acquired o, the constituents of most of the visibl heavenly bodies. [s. 229]