Motion picture projection; an elementary text-book (1921)

Record Details:

Title:
Motion picture projection; an elementary text-book
Date:
1921
Publisher:
New York, Theatre Supply Co.
Volume:
Motion picture projection; an elementary text-book
Leaf #:
000118
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
Date Added:
July 19, 2022
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MOTION PICTURE PROJECTION 117 LIGHT That light travels with a speed, which is much greater than the speed of sound is shown by the fact that the flash of a distant gun is always seen long before the sound of the report is heard and that lightning always precedes thunder. For most purposes it is sufficiently accurate to take the velocity of light as 186,000 miles per second. Light always travels out from a source in straight lines. Up till the year 1800, the Corpuscular theory of light was the one most generally accepted, that light consists of streams of very minute particles, or corpuscles projected with the enormous velocity of 186,000 miles per second from all luminous bodies. The facts of straight line propagation and reflection are exactly as we should expect them to be if this were the nature of light. A usual hypothesis which was first completely formulated by the great Dutch physicist — Huygens (1629-1695), regarded light like sound, as a form of wave motion. This hypothesis met at the first with two very serious difficulties; in the first place light, unlike sound, not only travels with perfect readiness through the best vacuum which can be obtained with an air pump, but it travels without any apparent difficulty through the great interstellar spaces which are probably infinitely better vacua than can be obtained by artificial means. If, therefore, light is a wave motion, it must be a wave motion of some medium which fills all space and yet which does not