IPC ch.17

wave

disturbance that transmits energy through matter or space

mechanical wave

created when a source of energy causes a vibration to travel through a medium (matter)

vibration

a repeating back and forth motion

electromagnetic waves (light)

do not require a medium

types of mechanical waves

transverse waves, longitudinal waves, and surface waves

transverse waves

perpendicular motion

crest

highest point of transverse wave

trough

lowest point of transverse wave

longitudinal waves

parallel motion

compression

particles in a medium are spaced close together

rarefaction

particles in a medium are spread out

surface waves

move in circles, occur at boundary between 2 different media

periodic motion

any motion that repeats at regular intervals

period

time required for 1 wave length to go by, represented by symbol T, si unit seconds

frequency

number of wavelengths in a given time (cycles per second), inversely proportional (INC frequency, DEC wavelength), symbol is, si unit is meters

speed formula

speed = wavelength x frequency (wavelength over period as well)

amplitude

the amount of particle vibration (distance from rest to crest), more energy, greater amplitude

reflection

the bouncing back of a wave as it meets a surface/boundary that it cannot pass through (no change of speed or frequency)

refraction

the bending of a wave as it enters a new medium at an angle (one side of the wave moves slower)

diffraction

bending of a wave as it moves around an obstacle or passes through a narrow opening

constructive interference

2 or more waves combine to produce wave with a larger displacement (add)

destructive interference

amplitudes are subtracted, 2 or more waves combine to produce smaller displacement (subtract)

standing wave

wave appearing to stay in one place, caused by interference between wave and it's reflection, has nodes and antinodes

nodes

no vibration on standing wave

antinodes

maximum vibration on standing wave

sound

longitudinal wave, speed depends on medium (fastest in solids > gases), s= 343 m/s in air

intensity

rate at which a wave's energy flows through a given area, depends on amplitude and distance from source

loudness

physical response to the intensity of sound

pitch

frequency of a sound as you perceive it, pitch=frequency

infrasound

sound @ frequencies lower than most can hear

ultrasound

sound @ frequencies higher than most can hear

light

visible light, speed = 3.0 x 10^8 m/s

electromagnetic waves

transverse waves consisting of changing electric fields and changing magnetic fields ( no medium needed)

doppler effect

object moving towards you, waves bunch causing higher frequency/moving away, waves stretch causing lower frequency

red waves

long with low pitch

blue waves

short and high pitch