BD also equals FE. Hence BD = NB, and since BC= of BD, it also equals of NB; that is, four thirds of NB equals the radius, and the angle NPB is the critical angle. The mathematical term for NB, when the radius PB equals unity, is the sine of the angle NPB; hence the critical angle is that angle, the sine of which multiplied by the index of refraction equals unity, or the sine of 90°. 38 19 Elasticity FORMULA 37 Motion (average speed or velocity) S = vt NUMBER 1 10 Aberration, 455, 471, 474. of liquids, 125. Air, absorption of heat, 258. liquefied, 266, 276. pressure of, 158-168. resistance of, 39. INDEX sound transmitted by, 195–199. wave motion in, 196. Air columns, vibration of, 224. Air thermometer, 243. Alternating current, 409. Alternator, 410. Ammeter, 380, 383. Ammonia, 277. Ampere, 354. Amplitude of oscillation or vibration, Becquerel rays, 516. 90, 192, 211. Aneroid barometer, 173. Bell, electric, 369; nodes and loops in, 224. Bichromate cell, 351. Bodies, defined, 10. Boiling, 273. Boiling point, 240. Boyle's Law, 177, 265. Bunsen photometer, 441. Cadmium Standard cell, 356. Calorimetry, 281-285. Capillary attraction, 125. Cells, galvanic, 347, 349. resistance of, 390. standard, 356. storage, 376. Center, of curvature, 449, 466. of gravity, 82. of moments, 58. of oscillation, 93. of percussion, 93. of pressure of liquids, 136. Centrifugal force, 63, 81. Charge, unit, 321. Charles, Law of, 265. current, 346. source of heat, 247. Chemical action, source of electric Convex mirror, 454. Chemical change, 9. Converter, electrical, 431. Copper wire table, 355. Couple, 60. Critical angle, 460. |