This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ...The change of direction experienced by a ray of light when it strikes a surface and is thrown back or reflected. Light is reflected according to two laws: (a) The angle of reflection is equal to the angle of incidence. (6) The incident and the reflected rays are both in the same plane which is perpendicular to the ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ...The change of direction experienced by a ray of light when it strikes a surface and is thrown back or reflected. Light is reflected according to two laws: (a) The angle of reflection is equal to the angle of incidence. (6) The incident and the reflected rays are both in the same plane which is perpendicular to the reflecting surface. Refraction. The change of direction which a ray of light undergoes upon entering obliquely a medium of different density from that through which it has been passing. In this case the following laws obtain: (a) Light is refracted whenever it passes obliquely from one medium to another of different optical density. (6) The index of refraction for a given substance is a constant quantity whatever be the angle of incidence. (c) The refracted ray lies in the plane of the incident ray and the normal. (d) Light rays are bent toward the normal when they enter a more refracted medium and from the normal when they enter a less refracted medium. A lens may be defined as a piece of glass or other transparent substance with one or both sides curved. Both sides may be curved, or one curved and the other flat. The object of the lens is to change the direction of rays of light and thus magnify objects or otherwise modify vision. Lenses may be classed as: Double convex Piano convex Concavo convex Double concave Piano concave Convexo concave The focus of a lens is the point where the refracted rays meet. Spherical Aberration. The reflected rays of concave spherical mirrors do not meet exactly the same point. This is called spherical aberration. Effect of Spherical Aberration. It produces a lack of sharpness and defination of an image. If a ground glass screen be placed exactly in the focus of a lens the image of an object will be sharply defined...
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