Phillips, Percy · London : T. C. & E. C. Jack ; New York : Dodge Pub. Co. · leaf 17
or rarefiedportion of air surrounded by undisturbed air will cast afairly definite shadow of itself on a screen placed closebehind it. For instance, if the shadow of a hot pokerbe received on a screen, the shadow of the hot air stream-ing upwards from the poker is seen quite distinctly.The hot air… … Fig. 2. PROPAGATION OF LIGHT 15 shadow of the colder denser air can be seen streamingoff downwards from the poker. Wood thereforearranged another spark so that it cast a shadow of thecompression produced by the first spark on to a photo-graphic plate. By adjusting the interval of timebetween the…
Light
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