An Elementary Treatise on OpticsJ. Smith, 1825 - 196 pages |
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Common terms and phrases
aberration angle of incidence aperture appears aqueous humour axis bright caustic centre chrystalline circle coincide colours concave lens converge convex lens crystal curve density diameter direction distant object ellipse equal equation experiment extreme eye glass field of view focal length foci fringes heliostat inches incident rays infinite distance instrument intersection inverted lamina of air latus rectum lenses luminous magnifying power magnitude measured medium molecules Newton object glass oblique observed Optics osculating circle parabola parallel rays pass pencil of rays perpendicular phænomena phænomenon plane mirror plate polarization principal focus prism produced radius ratio of refraction rays of light rays proceeding reflected rays reflector reflexion refracting power represented in Fig retina rings seen sine speculum sphere spherical spherical reflector substance subtended suppose surface tangent telescope thickness undulations vitreous humour
Popular passages
Page 108 - Do not the Rays of Light in falling upon the bottom of the Eye excite Vibrations in the Tunica Retina? Which Vibrations, being propagated along the solid Fibres of the optick Nerves into the Brain, cause the Sense of seeing.
Page 108 - When a Man in the dark presses either corner of his Eye with his Finger, and turns his Eye away from his Finger, he will see a Circle of Colours like those in the Feather of a Peacock's Tail.
Page 179 - The graduated circle ivhich regulates this motion should mark zero when the plane of the ring is perpendicular to the axis of the...
Page 4 - ... so contrived that, by means of adjusting screws, it may be made to turn the rays of the sun into the opening, and to give them a horizontal or any other required direction. The course of the rays is rendered palpable to the eye, by the illuminated particles of dust that are floating in the air.
Page 44 - The sine of the angle of incidence bears to the sine of the angle of refraction...
Page 108 - Do not these Colours arise from such Motions excited in the bottom of the Eye by the Pressure and Motion of the Finger, as, at other times are excited there by Light for causing Vision? And do not the Motions once excited continue about a Second of Time before they cease? And when a Man by a stroke upon his Eye sees a flash of Light, are not the like Motions excited in the Retina by the stroke?
Page 184 - ... varies as the square of the cosine of the angle between the plane of transmission of the analyser and the plane of the polariser.
Page 110 - ... would be somewhat laborious : probably the image, thus corrected, would approach very nearly to the form of the twelfth curve. To find the place of the entrance of the optic nerve, I fix two candles at ten inches distance, retire sixteen feet, and direct my eye to a point four feet to the right or left of the middle of the space between them : they are then lost in a confused spot of light ; but any inclination of the eye brings one or the other of them into the field of view.
Page 153 - ... the molecules must have some peculiar modification of a periodical nature, such as to incline them alternately to be reflected and refracted after passing through certain spaces. Newton characterised this tendency to alternate reflexion and transmission, and designated the two states, by the phrases Jits of easy reflexion, and jits of ea.iy transmission.* 929.
Page 45 - Snell's sine law of refraction; ie. that the ratio of the sines of the angle of incidence and refraction is...