Elementary Treatise on Natural Philosophy, Volumen4

æther analyzer angle of incidence beam beats body bright lines called centre colours conjugate foci convex convex lens corresponding crystal curvature denote density 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 inverted lens lenses light liquid luminous point magnifying power medium mercury metres minimum deviation musical node normal number of vibrations object object-glass observer obtained octave optical ordinary parallel particles 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 angle sonorous spectra spectrum spherical string surface telescope temperature tion tone transmitted traversing tube velocity of sound vertical vibrations vibrations per second violet virtual image visual angle wave-front wave-length waves