Natural philosophy. Treatise 5 |
Загальні терміни та фрази
aberration achromatic angle of incidence aperture aplanatic apparent magnitude appear called centre choroid ciliary processes colours compound lens conjugate foci convergent pencil convex lens crown-glass crystal crystalline lens cylindric pencil direction distance of distinct distinct vision divergent pencil emergent rays equal extraordinary ray extreme rays eye-glass eye-piece focal length focus F focus of refracted geometric focus glass hence image m n imaginary focus inches incident pencil incident ray index of refraction intensity lenses luminous magnifying power membrane object object-glass optic nerve parallel rays pass perpendicular placed plane mirror plane of incidence plate point of incidence polarisation portion principal focus prism produce proportion radiant point radii radius rays incident rays proceeding reflected rays reflecting telescope reflexion refractive power retina screen seen shadow side sine of incidence spectrum spherical surface telescope tion transparent vergency vertex violet visual angle vitreous humour wave
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Сторінка 69 - If a convex lens, with a focal length less than the distance of distinct vision, is placed between the eye and an object situated in the focus of the lens, the rays of each pencil proceeding from any point in the object will emerge parallel, and an image of it will be seen distinct and magnified. 'The size of the image will be to that of the object as the distance of distinct vision to the focal length of the lens.
Сторінка 96 - An object seems to us to be up or down, according as we raise or lower the pupil of the eye in order to see it ; the very notion of up and down is derived from our feelings of movement, and not at all from the optical image formed on the back of the eye.
Сторінка 79 - It varies with the eye-piece employed, the ratio of the focal length of the object-glass to that of the eye-piece giving its exact amount.
Сторінка 69 - The size of the image will be to that of the object as the distance of distinct vision to the focal length of the lens.' The cause of the parallelism of the emergent rays and of the enlargement of the image may be thus explained : Let E be the eye, and mn the diameter of its pupil, and KW a small object placed at the least distance of distinct vision.
Сторінка 45 - If parallel rays be incident nearly perpendicularly upon a spherical refracting surface, the distance of the geometrical focus of refracted rays from the surface, is to its distance from the centre, as the sine of incidence to the sine of refraction.
Сторінка 70 - R' and W. Thus the whole image will exceed the object in the proportion of R'W' to RW ; but these lines are to one another as EM to CM, or as the distance of distinct vision to the focal length of the lens. The visual angle REW would be to the angle R'EW...
Сторінка 80 - Without stopping to prove the principle, we may say that the magnifying power is simply equal to the quotient obtained by dividing the focal length of the object-glass by that of the eye-lens. It is to be noted, however, that a magnifying power of unity is sometimes spoken of as no magnifying power at all, since the image appears of the same size as the object.