All waves are traveling disturbances which carry energy from place to place.
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Transcript of All waves are traveling disturbances which carry energy from place to place.
Ex 1 - An AM station broadcasts at a frequency of 1230 kHz and an FM station broadcasts at 91.9 mHz. What are the wavelengths of these two stations?
The compressed area in a longitudinal wave is called a compression. The area where particles are further apart is called a rarefaction.
A sound with a single frequency is a pure tone. Most healthy people hear in a range of 20 Hz to 20 000 Hz (20 kHz).
When sound travels through a long, slender solid bar, the speed v is:
v = √ Y/ρY is Young’s Modulus and ρ is density.
The power of a sound wave is measured in watts W. The intensity I of a wave is the power per unit area, W/ m2.
Ex 7 - 12 x 10-5 W of sound power passes perpendicularly through two surfaces; one of area 4.0 m2 and the other of area 12 m2. Find each sound intensity.
0 decibels means the sound intensity is at the threshold of human hearing, not that the intensity is zero.
Doppler Effect - apparent change in pitch when a sound maker or listener are moving with respect to each other.
Source moving toward stationary listener:
f’ = f[ 1/(1 - vs/v)]
Source moving away from
stationary listener:f’ = f[ 1/(1 + vs/v)]
listener moving toward stationary source:
f’ = f(1 + vO/v)
listener moving away from
stationary source:f’ = f(1 - vO/v)
Chapter 17 The Principle of Linear Superposition - When two or more waves are present at the same time at the same place, the resultant wave is the sum of the individual waves.
When waves are in phase they produce constructive interference. When they are out of phase they produce destructive interference.
When tones of two different frequencies are produced beats are heard where constructive interference takes place.
In a transverse standing wave pattern, the nodes are places that do not vibrate at all, and antinodes vibrate with maximum amplitude.