Gilbert light experiments for boys . the spectrum is formed, the surface of the water isstirred, the colors of the spectrum are mixed and the reflectedbeam is white. This proves again that white light is made upof all the colors of the spectrum. Interference. In a water wave the particles of water simplymove up and down, but the wave moves forward. A wave lengthis a hill and a hollow. If, now, two waves of exactly the same length come togetherin such a way that one is one-half wave behind the other (), the hill of one coincides with the hollow of the other, theparticles of water do not
Gilbert light experiments for boys . the spectrum is formed, the surface of the water isstirred, the colors of the spectrum are mixed and the reflectedbeam is white. This proves again that white light is made upof all the colors of the spectrum. Interference. In a water wave the particles of water simplymove up and down, but the wave moves forward. A wave lengthis a hill and a hollow. If, now, two waves of exactly the same length come togetherin such a way that one is one-half wave behind the other (), the hill of one coincides with the hollow of the other, theparticles of water do not move at all, and one wave destroys theother. This is called interference. The same thing occurs in light waves; two streams of wavesmay come together and destroy each other, that is, producedarkness. GILBERT LIGHT EXPERIMENTS 93 Colors by Interfer-ence. If a beam ofsunlight is allowed tofall on a soap film heldin a vertical positionon the end of a lampchimney (Fig. 144), itis found that the soapfilm when viewed byreflected light is. Crossed by horizontal Fig. 144. Colors in a soap film colored bands. These colors are formed by interference as follows: The soap film hastwo surfaces with water between, and when it stands on edgethe water runs toward the bottom and the film becomes a narrowprism. Now the light is reflected partly from the front film andpartly from the back film, and where the films are 1-4, 3-4, 5-4waves of red light apart, the red waves from the rear are 1-2,1 1-2, 2 1-2 waves behind the red waves from the front when theyenter your eye. These two sets of waves, then, interfere and de-stroy each other, and all that your eye sees is blue. Similarly a
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