148. General investigation of the effect of a responsive medium 244 149. Wave velocity in a responsive medium according to the 157. Reflecting powers of metals for waves of low frequency 158. Connexion between refractive index and density 266 268 161. Analytical representation of the rotation of the plane of 168. Photo-gyration in the magnetic field 169. Connexion between the Zeeman effect and magneto-gyration. 287 290 291 295 ᎪᎡᎢ . CHAPTER XIII. TRANSMISSION OF ENERGY. 172. Propagation of energy 173. Waves of pure compression or dilatation in a perfect fluid 174. Plane waves of distortion in an elastic medium PAGE 297 297 301 176. 177. 175. Sphere performing torsional oscillations in an elastic medium Waves diverging from a sphere oscillating in an elastic medium Divergent waves of sound. 301 303 305 178. Scattering of light by small particles 179. Transmission of energy by electromagnetic waves 305 310 PART I. CHAPTER I. PERIODIC MOTION. 1. The Simple Periodic Motion. A motion which is repeated at regular intervals of time is called a periodic motion. The simplest kind of periodic motion is that in which a particle moves in a straight line, in such a way that its distance, x, from a fixed centre satisfies the equation x = a sin ∞ (t − 0)........ (1), where is the time and a and are constants. The equation shows If the time t is increased by 2π/w, no change is made in the values of either a or u, so that after a time interval of 2/w the position and state of motion are the same. The period is called the "time of oscillation," the "periodic time," or simply the "period" of the motion. Its relation to the constant w is expressed by the equation: T = 2π/w. |