Otto Henker

Name: 1911 Encyclopædia Britannica, Volume 16 — Lens
Author: Otto Henker

1911 Encyclopædia Britannica, Volume 16… (1911)

Summary

“1911 Encyclopædia Britannica, Volume 16 — Lens”, published in 1911, is a work by Otto Henker. It explores elements such as lens, rays and plane.

Quotes from 1911 Encyclopædia Britannica, Volume 16… (Otto Henker)

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ When we speak of “object-points,” it is always understood that the rays from the object traverse the first surface of the lens before meeting the second. In the same way, images may be either real or virtual. If the image be behind the second surface, it is real, and can be intercepted on a screen. If, however, it be in front of the lens, it is visible to an eye placed behind the lens, although the rays do not actually intersect, but only appear to do so, but the image cannot be intercepted on a screen behind the lens. Such an image is said to be virtual. ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ The laws of optical representations were first deduced in their most general form by E. Abbe, who assumed (1) that an optical representation always exists, and (2) that to every point in the object-space there corresponds a point in the image-space, these points being mutually convertible by straight rays; in other words, with each object-point is associated one, and only one, image-point, and if the object-point be placed at the image-point, the conjugate point is the original object-point. ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ Theory of Optical Representation.—If a pencil of rays, i.e. the totality of the rays proceeding from a luminous point, falls on a lens or lens system, a section of the pencil, determined by the dimensions of the system, will be transmitted. The emergent rays will have directions differing from those of the incident rays, the alteration, however, being such that the transmitted rays are convergent in the “image-point,” just as the incident rays diverge from the “object-point.” With each incident ray is associated an emergent ray; such pairs are termed “conjugate ray pairs.” ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ If the observer desires a perfectly correct perspective impression of the object-relief the distance of the pivot of the eye from the representation copy must be equal to the nth part of the distance of the plane focused for from the entrance pupil, if the instrument has produced a nth diminution of the object-side representation. The pivot of the eye must coincide with the centre of the perspective, because all images are observed in direct vision. It is known that the pivot of the eye is the point of intersection of all the directions in which one can look. ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ The deduction of the cardinal points of a spherical glass lens in air from the relations already proved is readily effected if we regard the lens as a combination of two systems each having one refracting surface, the light passing in the first system from air to glass, and in the second from glass to air. ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ The optical centre of a lens is a point such that, for any ray which passes through it, the incident and emergent rays are parallel. The idea of the optical centre was originally due to J. Harris (Treatise on Optics, 1775) ; it is not properly a cardinal point, although it has several interesting properties. In fig. 13, let C1P1 and C2P2 be two parallel radii of a biconvex lens. Join P1P2 and let O1P1 and O2P2 be incident and emergent rays which have P1P2 for the path through the lens. Then if M be the intersection of P1P2 with the axis, we have angle C1P1M = angle C2P2M ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ It will be assumed that light, so long as it traverses the same medium, always travels in a straight line; and in following out the geometrical theory it will always be assumed that the light travels from left to right ”

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Source: Wikisource

Otto Henker, 1911 Encyclopædia Britannica, Volume 16… (1911)

“ By referring to the equations given above, it is seen that a thin convergent lens produces both real and virtual images of real objects, but only a real image of a virtual object, whilst a divergent lens produces a virtual image of a real object and both real and virtual images of a virtual object. The construction of a real image of a real object by a convergent lens is shown in fig. ”

Otto Henker

Summary

Quotes from 1911 Encyclopædia Britannica, Volume 16… (Otto Henker)

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