Modeling Wave Characteristics s1

PHYS 205

WaveWave ModelingModeling

Purpose:

 model transverse waves  identify and measure wave characteristics

Materials:

 “butcher” paper ( 5-7 feet long, 2-3 feet wide), stopwatch, meter stick, markers

Procedure:

Each group should have three members. A transverse wave may be modeled when the marker moves back and forth perpendicularly to the direction of the moving paper. If done carefully, you should see a nice consistent “wave shape” (watch out for shark fins!).

Place the large sheet of butcher paper on the lab table. One group member steadily pulls the paper across the table while another member moves the marker back and forth over the paper. The arm should swing freely as a pendulum. The third group member uses the stopwatch to measure the amount of time needed to sketch the wave motion across the entire length of paper.

 Record the total time of the wave motion on the paper.  Record the phase of the wave (radians).  Label, measure, and record the wavelength of the wave (cm).  Label, measure, and record the amplitude of the wave (cm).  Count the number of complete vibrations and divide by the total time to obtain the frequency of the wave (Hz).  Divide the total time by the number of complete vibrations to obtain the period of the wave (s).  Find the wave’s velocity by measuring the total distance the wave traveled and dividing this value by the total time (cm/s).  Now calculate the wave’s velocity by multiplying the calculated frequency of the wave by the measured wavelength. Compare this result with the velocity obtained using the total distance and time. Why might they be different?  Waves are represented mathematically by trigonometric functions. One appropriate mathematical representation, or formula, for wave motion is y = A sin (ωt + Φ), where y = the displacement of the medium from the equilibrium position at any time t, A = amplitude in distance units, ω = angular frequency in radians/sec such that ω = 2πf, and Φ = phase shift in radians (positive for “left shift” and negative for “right shift”).  Write the equation of your transverse wave on your paper. Check with a graphing calculator, if available, making sure the calculator has been set to radian mode.

Be sure to show all work and calculations on the butcher paper.