topic 6 Flashcards Preview

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Flashcards in topic 6 Deck (58):
1

what is the effect of each type of radiation based on

how much energy the wave transfers

2

what happens when low frequency waves pass through soft tissue

they don't transfer much energy and so mostly pass through soft tissue without being absorbed

3

why are high frequency waves dangerous

because they all transfer lots of energy and so can cause lots of damage

4

what is UV radiation damaging to

-surface cells, which can lead to sunburn and cause skin to age prematurely

5

what are the serious effects of uv radiation

it can cause blindness and an increased risk of skin cancer

6

give 2 examples of ionising radiation

gamma rays and X-rays

7

gamma and x-rays carry enough energy to do what ...

knock electrons off of atoms

8

how is ionising radiation dangerous

it can cause gene mutation, cell destruction or even cancer

9

what is radiation dose measured in

sieverts

10

what is radiation dose

a measure of the risk of harm from the body being exposed to radiation

11

what does the risk of radiation dose depend on

the total amount of radiation absorbed and how harmful the type of radiation is

12

what are optic fibres

thin glass or plastic fibres that can carry data from telephones or computers over long distances as pulses of visible light

13

how do optic fibres transmit data

by using visible light

14

how does light rays work by

reflection- the light rays are bounced back and forth until they reach the end of the fibre

15

why is visible light used in optic fibres

because it is easy to refract light enough so that it remains in a narrow fibre

16

how do you get a clearer x-ray image, what does it depend on

it depends on the amount of x-ray radiation that is absorbed through the body

17

what is x-rays and gamma rays used to treat

cancer

18

what can gamma radiation also be used as

a medical tracer- this is where a gamma-emitting source is injected into the patient, and its progress is followed around the body

19

how do radiographers keep safe from x-ray and gamma radiation

they stand behind a lead screen, wear lead aprons or leave the room

20

what do fluorescence light generate and what is it re-emitted as

UV radiation- which is absorbed and re-emitted as visible light by a layer of phosphorus on the inside of a bulb

21

why are fluorescence lights good

because they are energy-efficient and and can be used when light is needed for a long period of time

22

what can security pens used to do

used to mark properties with names and can only glow under UV light

23

what is uv radiation produced by

the sun

24

what does communication to and from satellites use

microwaves

25

if you want to use microwaves for communication what do the microwaves need to pass through

the earth's watery atmosphere

26

in microwave ovens what do the microwaves need to be absorbed by

water molecules in the food

27

absorbing IR radiation causes objects to what ...

become hotter

28

what can IR radiation be used for

-cameras to see detect houses or objects and electric heaters

29

what are EM waves made up of

oscillating electric and magnetic fields

30

what type of current is made up of oscillating charges

alternating currents

31

as charges oscillate, what do they produce

oscillating electric and magnetic fields or electromagnetic fields

32

what are radio waves mostly used for

communication

33

when waves travel through a medium what happens to the particles

the particles of the medium oscillate and transfer energy between each other

34

what is the wavelength

the distance between the trough of one wave and the trough of wave next to it

35

what is the frequency

the number of complete waves passing a certain point per second

36

describe the oscillations in transverse waves

they are perpendicular (at 90 degree angles) to the direction of energy transfer

37

give 3 examples of transverse waves

-all electromagnetic waves
-ripples and waves in water
-a wave on a string

38

describe the oscillations in longitudinal waves

the oscillations are parallel to the direction of energy transfer

39

give an example of a longitudinal wave

a sound wave in the air

40

name the 3 things that can happen when a wave meets a boundary between 2 materials

1) the wave is ABSORBED by the second material
2) the wave is TRANSMITTED through the second material
3) the wave is REFLECTED

41

electromagnetic waves are what type of waves

transverse waves

42

what are electromagnetic waves vibrations of

electric and magnetic fields , this means that they can travel through a vacuum (space)

43

from the start of the EM wave spectrum, describe the frequency and the wavelength

it has a long wavelength and low frequency

44

at the end of the EM wave spectrum, describe the frequency and the wavelength

it has a short wavelength and high frequency

45

what is refraction

when waves hit a boundary at an angle and change direction

46

what happens when a wave crosses boundary between 2 materials

it changes speed

47

what is the optical density of a material

a measure of how quickly light can travel through a material

48

what is wave speed

the speed at which the wave moves through the medium (i.e. the speed at which energy is transferred)

49

1Hz=

1 wave per second

50

wave speed (m/s)=

frequency (Hz) X wave length (m)

51

how can we make sure that the results are accurate for reaction times (3)

-take results and remove any results that are anomalous -calculate mean value
-more people with timers

52

how can we reduce the problem of pressing the timer at correct times

by increasing the distance between the 2 people

53

what happens to waves when they change direction

it changes speed

54

when light passes from air into glass what happens

the velocity of light decreases (the light waves slow down.)

this causes the direction of the wave to change

55

when waves slow down they ...

bend towards the normal

56

what happens when ...
waves pass from the glass back to the air

their velocity increases- the light waves speed up

57

what happens when waves speed up

they bend away from the normal

58

when can refraction happen

when any wave changes speed as it passes from one medium to another