waves Flashcards
what is displacement?
the distance that a certain point in the medium has moved from its rest position
peak
the highest point above the rest position
trough is lowest
amplitude
the maximum displacement of a point of a wave from its rest position
wavelength
distance cocered by a fully cycle of the wave, usually from peak to peak or trough to trough
frequency
the number of waves passing a point each second
time period of a wave
1/frequency
wave speed
frequency x lamda (wavelength)
how does sound reach a persons ear drum?
the air is made up of many tiny particles. when sound is created, the air particles vibrate and collide with each ither, causing the vibrations to pass between air particles. the vibrating particles pass the sound through to a persons ear and vibrate the ear drum
what is the general name for waves that require a medium to vibrate?
mechanixal
what is the speed of sound in air and water?
330 m/s in air
1500 m/s in water
what are longitudinal waves?
in lonqitudinal waves, the vibrations are parallel to the direction of wave travel
what are some examples of longitudinal waves?
sound waves
ultrasound waves
seismic p-waves
longotudinal waves show areas of ______ and _________
compression
rarefaction
compressions
are regions of high pressure due to particles being close together
rarefactions
are regions of low pressure due to particles being spread further apart
what is a transverse wave?
the vibrations are perpendicular to the direction of wave travel
examples of transverse waves
- electromagnetic waves
ripples on water
seismic s-waves
what are electromagnetic waves
their vibrations or oscillations are changes in electrical and magnetic fields at right angles to the direction of wave travel
all electromagnetic waves can:
transfer energy as radiation from the source of the waves to an absorber
can travel through a vaccum
em spectrum from longest to shortest
radio, microsaves, infared, visible light, ultraviolet, xrays, gamma rays
red light has ___________. violet light has ________
red light has the lowest frequencies of visible light
violet has the highest
radio waves
do not cause damage when absorbed by the human body
used for communications
television
radio
microwaves
high frequency microwaves are absorbed easily into the food. the internal energy of the molecules increases when they absorb microwaves, which xauses heating
infared
used by electrical heaters, cookers for cooling food, infared cameras
visible light
it is used in fibre optix communications
ultraviolet
cannot be seen by humans
causes tans
causes skin cancer
xrays
internal imaging
absorbed by dense structures like bones
ionising radiation
xrays and gamma rays can add or remove electrons from molecules, producing electrically charged ions
- UV can cause premature aging and skin cancer
- x and gamma rayscan cause the mutation of genes (cancer)
the law of reflection states that
angle of incidence = angle of reflection
they are measured between the light ray and the normal
explain refraction
the density of a material affects the speed that a wave will be transmitted through it. in general, the denser the transparent material, the more slowly light travels through it
if a wave slow down, it‘s ______
wavelength will decrease
what happens to a light eay when it travels from water into air?
it bends away from the normal
which term is used to refer to the scattering of light by a rough surface?
diffuse reflection
which term is used to refer to regular reflection from a smooth surface in a single direction?
specular reflection
sound waves
ok
the speed of sound depends on the _____
medium through which it is travelling
how does the mechanism of the ear detect sound
sound waves enter the ear canal and cause the eardrum to vibrate. three small bones transmit these vobrations to the cochlea. this produces electrical signals which pass through the auditory nerve to tje brain, where they are interpreted as sound
what is sound above 20 000 Hz called?
ultrasound
uses of ultrasound
breaking kidney stones
cleaning jewellery
vibrations shake apart the dirt or kidney stones, breaking them apart
how does echo sounding work?
the time between a pulse of sound being transmitted and detected can be used to calculate the distance of the reflecting surface
seismic waves can cause
tsunamis and earthquakes
explain what happens to water waves as they pass into a deeper region
waves teavel faster in deeper water and more slowly in shallow water. they will soeed up so wavefronts move further apart
