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Waves and Sound

Waves and Sound. Chapter 16. 16.1 The Nature of Waves. A Wave: Traveling disturbance Carries energy from place to place Two Different Types: Transverse Longitudinal . Slinky. If the end is jerked up and down, an upward pulse is sent traveling toward the right.

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Waves and Sound

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  1. Waves and Sound Chapter 16

  2. 16.1 The Nature of Waves A Wave: • Traveling disturbance • Carries energy from place to place Two Different Types: • Transverse • Longitudinal

  3. Slinky • If the end is jerked up and down, an upward pulse is sent traveling toward the right. • If the end is then jerked down, a downward pulse is generated and also moves to the right.

  4. Transverse Wave • Wave in which the disturbance occurs perpendicular to the direction of travel of the wave. Ex. Radio waves, light waves, microwaves, guitars and banjo strings

  5. Longitudinal Wave • The disturbance occurs parallel to the line of travel of the wave. • Ex. Sound wave

  6. Transverse and Longitudinal • Some waves have both. • Water waves • Particles at the surface move on nearly circular paths.

  7. 16.2 Periodic Waves • Transverse and longitudinal waves are types of periodic waves. • Cycles or patterns that are produced over and over again by the source. • Cycle: • AmplitudeA: maximum excursion of a particle of the medium from the particle’s undisturbed position. Distance between a crest, or highest point on the wave pattern, distance between a trough, or lowest point on the wave pattern. • Wavelength: horizontal length of one cycle of the wave, horizontal distance between two successive crests.

  8. Period T: time required for one complete up/down cycle, just as it is for an object vibrating on a spring. Time required to travel one wavelength.Frequency: cycles per second or Hertz Hz

  9. Example Ex. One cycle of a wave takes one-tenth of a second to pass an observer, then ten cycles pass the observer per second. F = 1/(0.1s) = 10 cycles/s = 10 Hz

  10. Train example • Fig 16.6 • Train moves by at a constant speed v. The train consists of a long line of identical boxcars, each of which has a length and requires a time T to pass, so the speed is v = /T Same equation applies for a wave and relates the speed of the wave to the wavelength and the period T. Since the frequency of a wave is f = 1/T, the expression for the speed is

  11. Example 1: The Wavelengths of Radio Waves • AM and FM radio waves are transverse waves consisting of electric and magnetic disturbances traveling at a speed of 3.00 x 10^8 m/s. A station broadcasts an AM radio wave whose frequency is 1230 x 10^3 Hz (1230 kHz on the dial) and an FM radio wave whose frequency is 91.9 x 10^6 Hz (91.9 MHz on the dial). Find the distance between adjacent crests in each wave.

  12. The distance between adjacent crests is the wavelength . Since the speed of each waves is v = 3.00 x 10^8 m/s and the frequencies are known, the relation v = f can be used to determine the wavelengths.

  13. Slinky Experiment HOMEWORK Pg. 504 1, 2, 3, 4, 5

  14. Terminology Crest: the top of a wave Trough: the bottom of a wave Amplitude: how far the material is displaced from rest (from crest to trough) Wavelength: the length of one full wave (between two identical points, like two crests) Speed: how fast the wave moves Frequency: how many waves there are in a certain amount of time.

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