Chapter 11 Learning ObjectivesConcepts and Skills to Review
Period, frequency, angular frequency (Section 5.1, Section 10.6)
Position, velocity, acceleration, and energy in simple harmonic motion (Section 10.5)
Resonance (Section 10.10)
Graphical analysis of SHM (Section 10.7)
Summary
An isotropic source radiates sound uniformly in all directions. Assuming that no energy is absorbed by the medium and there are no obstacles to reflect or absorb sound,
In a transverse wave, the motion of particles in the medium is perpendicular to the direction of propagation of the wave. In a longitudinal wave, the motion of particles in the medium is along the same line as the direction of propagation of the wave.
A periodic wave repeats the same pattern over and over. Harmonic waves are a special kind of periodic wave characterized by a sinusoidal function (either a sine or cosine function).
If a periodic wave has period T and travels at speed v, the repetition distance of the wave is the wavelength:
λ = vT
(11-5)
The principle of superposition: When two or more waves overlap, the net disturbance at any point is the sum of the individual disturbances due to each wave.
A harmonic traveling wave can be described by
y(x,t) = A cos(ωt - kx)
(11-8)
The argument of the sinusoidal function, (wt ±kx), is called the phase of the wave at x and t. The constant k is the wavenumber
Reflection occurs at a boundary between media with different wave speeds. Some energy may be transmitted into the new medium and the rest is reflected.The wave transmitted past the boundary is refracted:
Coherent waves have the same frequency and maintain a fixed phase relationship with each other. Coherent waves that are in phase with each other interfere constructively; those that are 180° out of phase interfere destructively.
Diffraction occurs when a wave bends around an obstacle in its path.
In a standing wave on a string, every point moves in SHM with the same frequency. Nodes are points of zero amplitude; antinodes are points of maximum amplitude. The distance between two adjacent nodes is 1/2λ.
