Physics lecture: simple harmonic motion, waves and light

vibrations of longitudinal(repeating patterns of motion) sound waves or some other medium.

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

ex. 

sound waves

• repeating patterns of high and low pressures 
• (compresions and rarefactions)

the arrival of a compression

the arrival of a rarefaction.

refers to how often the particles of the medium vibrate when a wave passes through.

a number of complete back and forth vibrations of a particles through a medium per unit of time.

ex. F=1HZ/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).

Fspring=-Kx

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

• high intensity sound wave are loud
• high intensity light are bright

speed of all waves depends on the frequency and wavelength

• v=speed
• ;= wavelength
• t=period
• f=frequency

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

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

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

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.

I=P/A

SI units of sound intensity is power per unit area or W/m2

the sound source at the center of the sphere emits sound uniformly in all directions.

I=P/4TTr2

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.

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

the doppler effect for sound is recognized as a change in pitch when the sound is moving away (lower frequency) or low wavelength.

the doppler effect for light leads to a change in color.

refers to an object with sound that is not moving will have the same condensation (loudness waves)

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

Fo=V/lamda'= v/lambda-VsT

fo=fs(1/1-vs/v)

lambda'=lambda+VsT

Fo=V/lamda'= v/lambda-VsT

fo=fs(1/1+vs/v)