waves Flashcards
what do waves do
they transfer energy or informstion without transferring any matter
dif types of waves
MECHANICAL WAVES- sound, water and ones on springs
ELECTROMAGNETIC WAVES- light, radio and microwaves
whats a mechanical wave
a wave that travels through a substance
they can be either transverse or longitudinal waves
whats an electromagnetic wave
a wave that travels through a vaccum
they are transverse waves
whats a longitudinal wave
so they oscilate parralel to the direction the waves transfer energy
whats a transverse wave
this means that it oscillates perpendicular to the direction of the waves energy transfer creating ripples
whats the amplitude of a wave
biggest displacement from its orig position so the length of the hump from the middle, the longer the amplitude the more energy carried
whats a wavelength
distance from one bit of a wave to that same bit in the next wave
whats a frequency
amount of waves passing a fixed point per second
whats a period
amount of time it takes fo each wave to pass a fixed point
what is the wave speed equation
frequency x wavelength
how are waves relflected in a ripple tank
theyre reflected from a straight barrier at the same angle as the incident wave as their speed and wavelength do not change
whats refraction
change of a waves direction when they change medium, results in a slower speed
whats an incident wavefront
the initial waves that distinguishes them from the relfcted/refracted waves
what happens when something absorbs the waves that pass through it
the substance gains the energy and so is heated eg microWAVES
the amplitude of the wave decreases as its energy goes
formula for frequency
1/T
specular reflection
when the boundry is flat, it produces a clear image
whats diffuse reflection
when the boundry on surfaces is bumpy, cant see your reflection
in a more dense materials waves will bend..
towards the normal as the amplitude gets smaller
crest
Peak of 1 ossiclation
electromagetic waves
dont tranfer matter
transervse (perp oscillations)
electrogmagnetic spectrum order
radio
micro
infrared
visable
ultraviolet
x rays
gamma
speed of electrogmagnetic waves
300 million m/s
what happens as you go down the elctromagnetic spectrum
the wavelength decreases but as the speed stays the same the frequency icreases, this means that the waves become shorter and w more energy
white light properties
comes from lamps and the sun
contains all colours
infrared properties
all objects emit
hotter = more infrared radiation
absorbed into our skin
devices that use infrared radiation
remotes
scanners to detect radiation
to see people in dark through heat they emit
heats rooms and foods
uses of microwaves
carries satelite links, they can travel between space and earth and also spread out much less as they are shorter
heats food by penetrating and being absorbed by the water mollecules
shortest radio wave uses
tv broadcasting, carries more info
hazards of waves
infrared heats and kills skin cells
micro and radio penetrations bodies ad heats it enternally
mid length radio wave uses
carries local radio as they have a limited range
logest radio wave uses
carrkes national and international radio news as they have a much longer range as the WL is longer
quick explanation of how radio signals carry
- the microphoe is reached by sound waves and produces an audio signal, this is taken in waves to the transmitter as are carrier waves from a oscillator
- the audio signal modulates the carrier waves, these are supplied to the tramitter ariel which carries the signal
- the ariel recives the modulated AC which emits waves carrying the signal, it is then absorbed by the reciever
- the reciever then gets tje same oscillations through the curret as the frequency of the radio waves
- finally, the reciever separates the audio from the carrier waves and supplies the audio signal to a loudspeaker whihc can send out sound waves the same as the waves recieved by the microphone when it produced an audio signal
what are optical fibres
thin glass which tramsit signals carried by light and infrared radiation
pros of optical fibres
- light/ infrared has a shorter wavelength and so ca carry much more info
- signals stay in the fibre and so are more secure
dangerous of radiation/ UV rays
shorter and so more energy than visable light
harms human eye and can be blidning
too much from sun can cause cancer and perminently age the skin
low doses can cause canerous growth and gene mutation
reasons for sim propeties of x ray and gamma rays
both v short wavelengths so more ifo, less area convered and less range
carry lots of energy
how much can X/ gamma rays pass through
penetrate anything not too dense, can be stopped by thick lead
how do X and Gamma rays differ
x rays are produced whe electrons stop moving
gamma are produced when unstable nucleas release energy
gamma are shorter so can peentrate more w more energy
uses of gamma rays
- exposing food to it kills 99% of disease carrying orgnaisms
- surgical instruments can be 99% cleaned of bacteria to stop any risk of infection
- can be exposed to cancer cells- aimed just at the tumour can destroy it but not the surroudning tissue
ionisation meaning
when a high energy ray passes through a subatnce it can knock an electron off an atom giving it a pos charge- this can damage or kill the cell
how does an x ray occur
x ray tube is turned on, electros pass through the body part
they go strait through weaker areas but more dense sections are absrobed such as bones, making that part of the film lighter as it is not reached by the x rays which have been absrobed
theres a screen with a CCD senor that converts x rays to light, the light makes electronic signals that display a digital image
how to x ray a softer organ
the patients organ can be filled with a contrast medium which is a substance that will easily absorb the x rays
what does a radiation dose depend on
type of radiation used
how long body is exposed to it
eergy absrobed per sec by the body
dif between x rays used for images and destroying cells
therapy x rays have a smaller WL so they have a lot more energy and are more penetrating
lower energy imaging x rays can be absorbed by bones
examples of longitudinal waves
sound waves
seismic p waves
whats frequency measured in
hz
examples of transverse waves
electromagnetic
water
on a string
law of reflection
angle of incidece = angle of relfection
waves that carry signal
carrier waves
the shorter the wavelength of radio/microwaves
-more info carried
- shorter range
- less spread out
whats an oscillioscope
device that displays the amps frequency and voltage of a current
uses of uv radiation
flurosent lights
tanning beds
checking for invisible lights
sterilising water by destroying microorgnaisms
uses of visable light
cameras
optical fibres
whats fluroescnce
UV radiation being absorbed and then readmitted as visable light
