p5 waves Flashcards
what is a wave
a wave is an oscillation that transfers energy
what is a mechanical wave
this is a wave that requires a medium to travel through, eg sound waves
what are the two types of wave
longitudinal eg sound.
transverse waves eg the wave made on a string
whats the difference between transverse and longitudinal waves
longitudinal = the singular atoms vibrate parallel to the direction of energy transfer. transverse = the individual atoms vibrate perpendicular to the direction of the energy transfer.
what is the amplitude of a wave
the distance between the middle and the crest or trough. measured in metres or volts
what is the wavelength
the distant from one point on a wave to the same point on the next wave, measured in metres
what is frequency
the number of waves per second, measured in hertz
what is the time period
the time it takes for a wave to pass a point. measured in seconds.
what are the two ways to represent a wave.
time trace and and a snap shot. in a time trace it shows the displacement of the wave varies with time. a snapshot shows how displacement of the waves varies with distance.
whats the difference between snap shot and time trace of a wave.
on a time trace you can measure the period from one wave to the next.
on a snapshot you can measure the wave length
how can you model transverse waves
put a cork on some water and make small ripples.you will notice that the cork goes up and down but doesn’t follow the wave
how do you calculate wave velocity
Velocity = Wavelength X Frequency m/s = m X hz
how to find the velocity of ripples
use a ripple tank, you then have to find wavelength. do this with a ruler beneath the tank and take a photo. the measure the shadow. you can calculate the frequency by looking at the number of rotations on the motor. then just use the equation
how do the velocity of sound
use an oscilloscope. connect two microphones that are a certain distance apart. this machine measures the time it takes sound to travel from one microphone to another
why the speed of sound vary in different temperatures
because sound is a mechanical wave it travels by physically hitting other atoms. in warm temperatures this is more likely to happen.
what is refraction
this is when a wave changes velocity and therefor direction
what happens when a wave slows down / speeds up
slows down - bends towards the normal
speeds up - bends away from the normal
what is the normal
the line at 90 degrees to the surface
when the velocity increases what happens to wavelength and frequency
wavelength - increases
frequency - decreases
what three things can happen to sound at a boundary
reflects (an echo)
transmitted and possibly refracted
absorbed
what is ultrasound and what is it used for
this is sound with a frequency over 20,000 hz. humans cannot hear it. it can be used for medical imaging (babies and kidney stones)
also used for navigation in ships
how does the ear detect sound
sound waves are directed to the ear drum which vibrates. these vibrations are passed on and amplified by ossicles. it travels through the oval window. it then reaches the cochlea which contains a liquid that passes the vibrations on to small hairs. these small hairs are attached to sound detecting cells. chemical signals are sent to the brain which interprets it as sound.
what is natural frequency
the frequency in which an object vibrates easily
what is resonance
this is what happens when an object is vibrated at its natural frequency. it vibrates more violently
why do humans hear a range of frequencies
because within the ear are hairs that vibrate at different frequencies. the range of frequencies that we hear depend on the range of sizes of the hairs
