p5.2 Flashcards
what are sound waves created by?
and what do they transfer
- vibrating particles
- which collide with neighboring particles
- to transfer kinetic energy
what are EM waves created by?
and what do they transfer
- vibrating charged particles
- which transfer electromagnetic energy
in what direction does a magnetic and electric field travel in an EM wave?
electric- upwards
magnetic - to the right/left
mnemonic to remember order of EM waves?
rock music is very useful (for) experiment (with) Goats
what is the amplitude of EM radiation?
a measure of the light intensity (not energy)
equation to calculate wave speed?
c = f x λ speed = frequency x wavelength
m/s = Hz x m
give the 5 steps in which radio waves are produced
1) oscillating p.d applied across a wire
2) electrons oscillate backwards and forwards at same frequency
3) produces oscillating electrostatic and magnetic field
4) fields travel and cut across an ariel
5) electrons within ariel oscillate, producing an electrical signal
why do human beings give off infrared and not gamma waves?
as they are not hot enough (needs a greater light intensity - but do not have enough energy)
why do objects glow red hot?
so hot, that do not emit infrared (as humans do), but visible light (which has more energy)
how do infrared cameras work? - 4
- Thermal imaging cameras use infrared radiationto produce thermograms.
- A charge coupled device (CCD) absorbs the infrared radiation and displays it as visible colour.
- Different colours of visible light are used to indicate the different intensities of infrared radiation.
- The hotter a certain part of a medium,the more infrared light it will emit.
how would infrared radiation be used in medical imaging?
- when infected/injury, skin emits more infrared radiation (as is hot)
- so can see damaged areas
dangers of X-rays?
can cause cancer (has ionising power)
- ions from radiation react with cells and damage/kill them
how does X-Ray film work?
- darkens when radiation hits it
- so denser tissue/bones absorb the radiation
could a tissue partially absorb X-rays
yes, and then shown as grey on the film
why can EM waves be used to explore hidden structures within our bodies?
- how they react at boundaries
(ie. absorbed/reflected) - so an external detector can detect reflection to build up an image
how are gamma rays used for imaging?
as tracers (to see performance of an organ)
describe is more detail how gamma rats are used for imaging
- radioactive substance ingested by patient
- releases gamma rays
- distribution of gamma rays are picked up
why are gamma rays good for imaging?
high penetrating power, as it leaves the body it is easy to detect (low danger to the patient, as radiation leaves body)
are gamma rays used to show you structures of the body?
no, as they are given out in all directions
- so has a low + unclear resolution
how is exposure to radiation reduced in hospitals for doctors?
- leave the room
- wear lead aprons
- walls lined with thick lead
if there is poor blood flow within a patient, how would that be shown once they are injected with a radioactive tracer?
less gamma radiation emitted there
X ray imaging - 3
- X-rays will pass through soft tissue (low density medium),but are absorbed by bone (high density medium).
- X-rays that pass through the body, darken photographic film.
- The film remains white where X-rays were absorbed by the body and didn’t reach the film.
Gramma radiation + imaging - 5
- A radioactive tracer is a radioactive compound of an element.
- Radioactive tracers will (usually) emit gamma radiation.
- Radioactive tracers are ingested by/injected into a patient and quickly enter the bloodstream and organs.
- The intensity of the gamma radiation being emitted is monitored outside by a camera.
- Where there is poor blood flow inside the body, less gamma radiation will be emitted there, and this indicates a possible health problem.
