Essentials of Modern Physics (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 Excerpt: ...yields a note of its lowest possible pitch. Such a note is called its fundamental; it is produced when a string, Fig. 256, is plucked or bowed near the middle. The sonometer is an apparatus used in the laboratory for the study of vibrating strings. Suppose Fig. 256.--String vibrating as, .., .. a whole sounds fundamental. we divide a sonometer string into eight equal parts and put Vshaped paper riders on the string in the positions shown at 1, 2, 3, 4, and 5 of Fig. 257. If we touch the string at C and then bow it at D, the riders at positions 1, 3, and 5 will be thrown off. Those at 2 and 4 will not be disturbed. The experiment shows that the string is now vibrating in four parts, or segments. That portion of the string included between A and B, Fig. 258, is called a loop or segment. The points where no vibration occurs are called nodes. A I I & I c D v One of the most interesting 1 rrJA things about this experiment arises Fl. 257ieSXEtsvibratin, t from the fact that the pitch is increased until it is two octaves higher than the fundamental. A note whose vibration rate is a multiple of that of the fundamental is called an overtone, or harmonic. When a string vibrates in two segments, the first overtone is produced; its pitch is an octave above the fundamental. The second overtone has a frequency three times that of the fundamental; the second overtone of C is the note G'. The third overtone has a vibration A B f 'Z--K&z& r: 1 rate four times that of the funda T, mental, and so on. Tig. 258.--Loops and nodes. 293. Quality. It is easy to pick out the various instruments in an orchestra, although the pitch may be the same. Two persons may sing true to pitch and yet the voice of one may be the more pleasing. The quality of a sound depen...