A mathmatical description of a wave.

The displacement (in meters) of a wave is y= 0.26 sin((pie)t-3.79(pie)x, where t is in seconds and x is in meters. (a) Is the wave traveling in the +x or-x direction? (b) What is the displacement of y when t= 38s and x=13m?

Sound Intensity

A rocket in a firework's display explodes high in the air. The sound speeds out uniformly in all directions. The intensity of the sound is 2.0 x 10^-6 W/m^2 at a distance of 120 m from the explosion. Find the distance from the source at which the intensity is 0.80 x 10^-6 W/m^2.

Decibels

The volume control on a stereo amplifier is adjusted so the sound intensity level increases from 23 to 61 dB. What is the ratio of the final sound intensiry to the original sound intensity?

Concept question

(a) When sound emerges from a loadspeaker, is the diffraction angle determined by the wavelength, the diameter of the speaker, or a combination of these two factors?(b) How is the wavelength of a sound related to its frequency ? Explain your answers. Problem The following two lists give diameters and sound frequencies for three loudspeakers. Par each diameter with a frequency, so that the diffraction angle is the same for each of the speakers. The speed of sound is 343 m/s. Find the common diffraction angle. Diameter, D .050m .10m .15m Frequency, f 6.0 kHz 4.0 kHz 12.0 kHz

Periodic waves : Calculating frequency and speed.

Suppose that 15 boxcars on a freight train pass by in a time of 12.0 seconds and each has a length of 14.0 m. (a) What is the frequency at which each boxcar passes? (b) What is the speed of the train?