Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . le which the incidentray makes with the normal, theangle of incidence; and theangle which the refracted raymakes with the normal, theangle of refraction. That is,referring to Fig. 2, ^ (7 is theincident ray; CB, the refractedray: D E, drawn perpendicularto the surface of the media, F G, the normal; A CI), the angle which A Cmakes withthis normal, the angle of incidence; and B C E, the angle which B C makes with thenormal, the angle of refraction.—Henry M. MIntir
Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . le which the incidentray makes with the normal, theangle of incidence; and theangle which the refracted raymakes with the normal, theangle of refraction. That is,referring to Fig. 2, ^ (7 is theincident ray; CB, the refractedray: D E, drawn perpendicularto the surface of the media, F G, the normal; A CI), the angle which A Cmakes withthis normal, the angle of incidence; and B C E, the angle which B C makes with thenormal, the angle of refraction.—Henry M. MIntire, M. E. A strong, high light affects the chemical substances used in photography much morerapidly and powerfully, comparatively speaking, than a mellow, diffused, or the point will be better understood by considering the following mathematicalformula: Let the high-light be equal to one hundred; then black, as the absence of alllight, theoretically at least, will be equal to 0; half-light will be equal to fifty ; quarter,equal to twenty-five; and so on. Now let ten seconds be the time required for the high-. LIGHT. 29 lu the construction of lenses advantage is taken of this quality of light bythe use of optical glass varying in density, thus securing the whitest possiblelight, or achromatism. Dispersion is the separation of a beam of white light into its componentrays which vary from each other in color and in refrangibility. The prism disperses the rays of light and creates the solar spectrum. Theclouds scatter the rays of the sun and produce the glories of sunset andsunrise. When a narrow beam of light is admitted into a darkened room it willillumine an object close to the point of entry. Remove the object further andfurther away, soon it ceases to be visible. This is because of the absorption ofthe light. Some surfaces, like velvet, coarse papers, and fabrics absorb light. 11. Understanding fairly these varied qualities of light, we shall see, as wego on
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