Elementary Treatise on Natural Philosophy, Volumen4

achromatic achromatic lens angle of incidence beam body bright lines called centimetre centre coincidence collimator colours concave lens concave mirror conjugate foci consists continuous spectrum convex convex lens corresponding crystal curvature dark lines denote direction displacement distance distinct vision emitted employed equal experiment eye-piece flame focal length glass Hence Iceland-spar illuminated incident ray increase index of refraction instrument interval inverted image lens lenses luminous point magnifying power medium microscope minimum deviation naked eye normal object object-glass observer obtained octave optical ordinary parallel particles pass pipe pitch placed plate polarization portion position principal axis principal focus prism produced propagation pupil ratio refrangible represented retina rotation screen seen slit solar spectrum solid spectra spectroscope spherical string sun's surface telescope temperature tion tone traversing tube velocity of light velocity of sound vibrations vibrations per second virtual image visual angle wave-length waves