Physics lecture: simple harmonic motion, waves and light
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Define sound waves
vibrations of longitudinal(repeating patterns of motion) sound waves or some other medium.
Sound waves in the air
pressure waves that move back and forth, producing a series of compression (high pressure) and rarefactions(low pressure) to produce a longitudinal sound wave.
vibrations of particles of a medium
regions of high air pressures
regions of low air pressure
a disturbance of a medium that comes from a distance and travels in one complete wave cycle.
the measurement of one wave crest to the next adjacent wave crest. vibrations are perpendicular to the direction of motion.
looks like roller coaster track.
ex. water waves or sting waves
- light is known as an electromagnetic wave
- light does not require a medium
- light is a transverse wave
repeating patterns of compression and rarefactions. vibrations are in the direction of motion.
looks like a spring
***speed of sound***
- repeating patterns of high and low pressures
- (compresions and rarefactions)
High pressures in pressure waves
the arrival of a compression
low pressures in pressure waves
the arrival of a rarefaction.
***frequency of sound***
refers to how often the particles of the medium vibrate when a wave passes through.
Frequency of a wave
a number of complete back and forth vibrations of a particles through a medium per unit of time.
- the periodic motion of a motion that repeats itself
- A restoring force is responsible for the periodic motion
- Restoring force is proportional to the displacement
For certain springs, the amount of force is directly proportional to the amount of stretch or compression (x); the constant of proportionality is known as the spring constant (k).
If a spring is not stretched or compressed, then there is no elastic potential energy stored in it.
wave transport energy
- high waves----high energy
- low waves---low energy
intensity of a wave depends of the amplitude
- high intensity sound wave are loud
- high intensity light are bright
speed of all waves depends on the frequency and wavelength
- ;= wavelength
the propagation of longitudinal waves of high compressions and regions of rarefactions
ex. tuning forks form longitudinal waves
sound spectrum has few frequencies and can be divided into three frequency regions.
- infrasonic f<20hz
- audible, 20hz<f<20khz
- ultrasonic, f>20khz
Longitudinal sound waves
sound is a longitudinal wave that is created by a vibrating object. It can be created or transformed only in a medium and cannot exist in a vacuum
a region of increased pressure (a compressed spring)
a region of released pressure.
the production of an inward motion when the air pressure is slightly less than normal
frequency of a sound wave
is the number of cycles per second that passes by a given location.
a sound with a single frequency
ex. telephone push buttons
the amount of energy transported per second by a sound wave is called the power of the wave and is measured in SI units of joules per second or watts
sound intensity and distance
intensity decreases with distance from the source (I/r2)
the sound power P that passes perpendicularly through a surface divided by the area A of that surface.
SI units of sound intensity is power per unit area or W/m2
spherically uniform radiation
the sound source at the center of the sphere emits sound uniformly in all directions.
a decibel is a unit in measuring the sound intensity level
greater intensities give rise to louder sounds,but doubling the intensity does not double the loudness.
doppler effect when sound approaches
the apparent change in frequency resulting from the relative motion of the source and the observer as sound approaches (higher frequency) or high wave lengths
doppler effect as sound leaves
the doppler effect for sound is recognized as a change in pitch when the sound is moving away (lower frequency) or low wavelength.
doppler effects in lights
the doppler effect for light leads to a change in color.
sources standing still
refers to an object with sound that is not moving will have the same condensation (loudness waves)
sources that are moving
refers to an object with sound is moving toward a person the wavelength will get smaller
wave length moving away from a person, the wavelength becomes larger apart
lambda '= lambda-VsT
sources moving toward a stationary observer
source moving away from stationary observer
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