p5.2

Question 1

what are sound waves created by?

and what do they transfer

Answer 1

• vibrating particles
• which collide with neighboring particles
• to transfer kinetic energy

Question 2

what are EM waves created by?

and what do they transfer

Answer 2

• vibrating charged particles

- which transfer electromagnetic energy

Question 3

in what direction does a magnetic and electric field travel in an EM wave?

Answer 3

electric- upwards

magnetic - to the right/left

Question 4

mnemonic to remember order of EM waves?

Answer 4

rock music is very useful (for) experiment (with) Goats

Question 5

what is the amplitude of EM radiation?

Answer 5

a measure of the light intensity (not energy)

Question 6

equation to calculate wave speed?

Answer 6

c = f x λ 
speed = frequency x wavelength 

m/s = Hz x m

Question 7

give the 5 steps in which radio waves are produced

Answer 7

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

Question 8

why do human beings give off infrared and not gamma waves?

Answer 8

as they are not hot enough (needs a greater light intensity - but do not have enough energy)

Question 9

why do objects glow red hot?

Answer 9

so hot, that do not emit infrared (as humans do), but visible light (which has more energy)

Question 10

how do infrared cameras work? - 4

Answer 10

• 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.

Question 11

how would infrared radiation be used in medical imaging?

Answer 11

• when infected/injury, skin emits more infrared radiation (as is hot)
• so can see damaged areas

Question 12

dangers of X-rays?

Answer 12

can cause cancer (has ionising power)

- ions from radiation react with cells and damage/kill them

Question 13

how does X-Ray film work?

Answer 13

• darkens when radiation hits it

- so denser tissue/bones absorb the radiation

Question 14

could a tissue partially absorb X-rays

Answer 14

yes, and then shown as grey on the film

Question 15

why can EM waves be used to explore hidden structures within our bodies?

Answer 15

• how they react at boundaries
  (ie. absorbed/reflected)
• so an external detector can detect reflection to build up an image

Question 16

how are gamma rays used for imaging?

Answer 16

as tracers (to see performance of an organ)

Question 17

describe is more detail how gamma rats are used for imaging

Answer 17

• radioactive substance ingested by patient
• releases gamma rays
• distribution of gamma rays are picked up

Question 18

why are gamma rays good for imaging?

Answer 18

high penetrating power, as it leaves the body it is easy to detect (low danger to the patient, as radiation leaves body)

Question 19

are gamma rays used to show you structures of the body?

Answer 19

no, as they are given out in all directions

- so has a low + unclear resolution

Question 20

how is exposure to radiation reduced in hospitals for doctors?

Answer 20

• leave the room
• wear lead aprons
• walls lined with thick lead

Question 21

if there is poor blood flow within a patient, how would that be shown once they are injected with a radioactive tracer?

Answer 21

less gamma radiation emitted there

Question 22

X ray imaging - 3

Answer 22

• 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.

Question 23

Gramma radiation + imaging - 5

Answer 23

• 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.