. Light, a textbook for students who have had one year of physics. valent to a right-handed and a left-handed circular vibration, each having half the amplitude ofthe linear vibration. This can be done analytically, by theuse of equations, but the following graphical method is perhapsbetter. A right-handed circular motion can be represented by avector, whose length is equal to the radius of the circle, andwhich swings at a uniform rate aboutthe origin, like the vector OA in figure120, that is, the end of the vector al-ways gives the position of the bodyundergoing the circular motion. Aleft-han
. Light, a textbook for students who have had one year of physics. valent to a right-handed and a left-handed circular vibration, each having half the amplitude ofthe linear vibration. This can be done analytically, by theuse of equations, but the following graphical method is perhapsbetter. A right-handed circular motion can be represented by avector, whose length is equal to the radius of the circle, andwhich swings at a uniform rate aboutthe origin, like the vector OA in figure120, that is, the end of the vector al-ways gives the position of the bodyundergoing the circular motion. Aleft-handed circular motion would besimilarly represented by a vectorswinging in the opposite rule for compounding two vectorsis to place the origin of one at the ter- t/minus of the other. Therefore, to com-pound a left-handed with a right-handed circular motion, we take theterminus. A. of the latter for the center about which the former,AB, turns. Now if OA swings at a uniform rate to the rightwhile AB swings at a uniform rate to the left from the end of. Figure 120 232 LIGHT OA. the point B will describe the path of a point whose motionis a combination of the two circular motions. If OA and AB areequal in length, and if they both rotate at the same rate, thispath is the straight line CD, as can be easily proved by simplegeometry. It is also easy to prove that the motion is simple-harmonic, with amplitude twice the radius of either plane-polarized beam of light can therefore be regardedas composed of two circularly-polarized components of the sameperiod but half the amplitude, one right-handed, the other left-handed. According to Fresnels hypothesis, these, on enteringthe quartz along the optic axis, will travel through it withdifferent velocities. On emerging into the air again, one ofthese components will have gained on the other in phase, be-cause of its greater velocity, and this gain in phase causes theplane-polarized beam to which the two on emergence a
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectlight, bookyear1921
