# Physics, Chapter 25

## Terms

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Vibration
A wiggle in time.
Wave
A wiggle in space and time.
Period
The time of a back and forth swing or a simple period of time from the beginning of something to the end.
Simple Harmonic Motion
The back and forth vibratory motion of a swinging pendulum.
Sine Curve
Pectorial representation of a wave.
Crest
High point of a wave.
Trough
Low point of a wave.
Amplitude
The distance from the mid-point to the crest (or tough) of a wave.
Wavelength
The distance from the top of one crest to the top of the next one.
Frequency
How frequently a vibration occurs.
Hertz
Unit of frequency.
What is the source of all waves?
Something that vibrates.
If the frequency is 2 Hz, how much time is needed to complete one vibration? 3 Hz?
1/2 second, 1/3 second.
Sound
Energy that travels to our ears in the form of one kind of wave.
T/F - It is the disturbance that moves along the length of the string, not the parts of the string itself.
True
What determines the speed of a wave?
The medium through which it moves.
When is a wave a "transverse" wave?
Whenever the motion of the medium is at right angles to the direction in which a wave travels.
Examples of transverse waves?
In the stretched strings of musical instruments and upon the surfaces of liquids. Electromagnetic radio waves and light are also examples.
Longitudinal Wave
The particles move along the direction of the wave rather than at right angles to it.
Interference Pattern
Wave effects may be increased, decreased, or neutralized.
Consructive Interference
The result of a wave is increased amplitude.
Destructive Interference
Cancellation
T/F - Interference is a characteristic of all sound waves.
False, it is a characteristic of all wave motion in general.
Node
The parts of a rope on a standing wave that remain stationary.
Anti-Nodes
The positions on a standing wave with the largest amplitudes are known as antinodes.
T/F - Standing waves can be produced in transverse and sound waves.
False, standing waves can be produced in transverse or longitudinal waves.
Doppler Effect
The change in frequency due to the motion of the source. The greater the speed of the source, the greater will be the Doppler effect.
Blue Shift
An increase in frequency, named so because of the fact that the increase is toward the high-frequency, or blue, end color spectrum.
Red Shift
A decrease in frequency.
Supersonic
Faster than sound.
Shock Wave
A shock wave is produced by overlapping spheres that form a cone.
Sonic Boom
When the conical shell of compressed air that sweeps behind a supersonic aircraft reaches listeners on the ground below, the sharp crack they hear is described as a sonic boom.

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