Elementary Treatise on Natural Philosophy, Dio 4

æther analyzer angle of incidence beam beats body bright lines called centre colours concave mirror conjugate foci convex convex lens corresponding crystal curvature denote density diffraction direction displacement distance double refraction elasticity employed equal experiment eye-piece flame focal length frequency of vibration fundamental note glass harmonics Iceland-spar incident ray index of refraction interval lens lenses luminous point magnifying power medium minimum deviation musical nearly node normal number of vibrations object object-glass observer obtained octave optical ordinary parallel particles pass perpendicular pipe pitch placed plate polarization portion position principal axis principal focus prism produced propagation rarefaction ratio reflected ray refrangibility represented retina rotation screen seen slit solar solid solid angle sonorous spectra spectrum spherical string surface telescope temperature tion tone transmitted traversing tube undulation velocity of sound vibrations vibrations per second virtual image visual angle wave-front wave-length waves