1. Two waves have the same frequency and wavespeed but
different phases and amplitudes. The first has an amplitude of 4.00 mm and a
phase is pi/6, while the second has amplitude of 3.0 mm and a phase of pi/2.
(a) Draw phasors that represent these two waves, and show the phasor that represents
the sum of these two waves.
(b) What are the amplitude and phase of the sum?
2. Cummings et al., p. 507, ch. 17, Problem 51.
3. A 1000 Hz sound in air has an intensity of 5 x 10-9
W/m.
This is the equation [Eq. 18-15, p. 521] for the intensity of a wave as a function
of the density of the material, the wave speed, the angular frequency, and the
displacement amplitude: 
(a) Write Eqn. 18-15 for average power in terms of pressure amplitude, ÜPaxm
instead of displacement amplitude, sm = S.
(b) Find ÜPmax and S = smax for this sound.
(c) I want a 20 Hz sound with the same intensity. What is S = smax
for this sound?
4. Do the worksheet: “Applets: Reflection and Refraction”
This page maintained by Anne G. Young. Last modified 20-Apr-2005 .