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?
a measure of the light intensity (not energy)
- the light intensity is proportional to the amplitude, but it is not necessarily equal to it
equation to calculate wave speed?
v = f x λ speed = frequency x wavelength
m/s = Hz x m
give the 4 steps in which radio waves are transferred between an antenna and an aerial
1) oscillating p.d applied across a wire, charge oscillates up and down the antenna
2) produces oscillating radio waves at same freq, which travel through the air to…
3) aerial absorbs radio waves
4) which induce an alternating electric current of the same frequency in the ariel
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?
use pixels in a charged-coupled device (CCD) which are receptive to infrared radiation (and produce colours depending on intensity)
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? (3)
- are not fully absorbed by skin (penetrates skin)
- and may be absorbed/reflected by other structures within the body
- 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 rays 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? (3)
- leave the room
- wear lead aprons
- walls lined with thick lead
