P7: Radioactivity

Question 1

what is the piece of equipment used to detect and count radioactivity

Answer 1

Geiger counter

Question 2

what are the three types of radiation

Answer 2

alpha, beta and gamma

Question 3

why are some substances radioactive

Answer 3

they have an unstable and decaying nucleus

Question 4

how does a nucleus become stable again

Answer 4

emitting any type of radiation

Question 5

the process of a nucleus becoming unstable is….

Answer 5

random

Question 6

what is an isotope

Answer 6

atoms of the same element that have different numbers of neutrons

Question 7

what is an alpha particle made of

Answer 7

two protons and two neutrons

Question 8

what happens when an alpha particle is emitted

Answer 8

-atomic number -2, mass number -4
-mass and charge reduced

Question 9

what is a beta particle

Answer 9

a fast moving electron

Question 10

how does a beta particle affect mass and atomic number

Answer 10

mass number -1
charge overall -1

Question 11

what is gamma

Answer 11

electromagnetic wave

Question 12

what is the effect of gamma on the mass and atomic number

Answer 12

everything is unchanged

Question 13

which radiation sometimes emits a neutron

Answer 13

alpha, due to particles colliding with the unstable nuclei. this makes it easier for it to pass through substances, as neutrons are uncharged

Question 14

alpha penetration and range

Answer 14

thin sheet of paper, range is 5cm

Question 15

beta penetration and range in air

Answer 15

aluminium sheet (5mm) or lead sheet (2-3mm), range is about 1m

Question 16

gamma penetration and range in air

Answer 16

thick lead sheet (several cms) and concrete (>1m), range is unlimited as it spreads out in air without being absorbed

Question 17

what is the word for when an object is exposed to ionising radiation

Answer 17

irradiated, it does not become radioactive

Question 18

what is radioactive contamination

Answer 18

radioactive material is deposited on or in an object/person

Question 19

one machine that uses radiation that could be harmful

Answer 19

x-ray

Question 20

how can we reduce our exposure

Answer 20

-keeping as far away as possible from the source
-spending as little time
-shielding themselves with thick concrete/lead plates

Question 21

what is alpha radiation used for

Answer 21

smoke alarms

Question 22

why is alpha used for smoke alarms

Answer 22

ionise in air and are weak penetrators, allowing them to interact with smoke particles. this disrupts the flow or ions between the charged plates and triggers the alarm

Question 23

why is alpha more dangerous in the body than beta or gamma

Answer 23

highly ionising, easily absorbed by cells

Question 24

what is beta used for

Answer 24

automatic thickness monitoring in metal foil production

Question 25

what is activity

Answer 25

the activity of a radioactive source in the number of unstable atoms in the source that decay per second

Question 26

unit of activity

Answer 26

Becquerel (Bq)

Question 27

what is count rate

Answer 27

the number of counts per second

Question 28

what are the meanings of half-life

Answer 28

-average time it takes for the number of nuclei of the isotope in a sample to half -average time it takes for the count rate from the isotope in a sample to fall to half its initial value

Question 29

the count rate after n half-lives =

Answer 29

the initial count rate /2 to the power of n

Question 30

what are radioactive tracers

Answer 30

they are used to trace the flow of a substance through an organ. it emits gamma radiation that can be detected from outside the system.

Question 31

what does a patient do before radioactive tracers

Answer 31

drinks water containing a tiny amount of radioactive substance

Question 32

example of radioactive tracer

Answer 32

radioactive iodine to find out if a patient's kidney is blocked

Question 33

what are gamma cameras used for

Answer 33

take images of internal body organs

Question 34

HOW gamma camera

Answer 34

before, patient injected with solution of gamma-emitting radioactive isotope. this is absorbed by organ. camera detects the radiation emitted. it makes an image by only detecting nuclei directly in front of it.

Question 35

what can gamma be used for treatment-wise

Answer 35

narrow beam to destroy cancerous tumours

Question 36

what is a radioactive implant

Answer 36

beta or gamma emitting isotopes are used to form small seeds or rods. they are given short-ish half-lives and destroy cancer cells

Question 37

what do we get radiation from

Answer 37

-air (radon) -medical -ground -food and drink -cosmic

Question 38

what is nuclear fission

Answer 38

the splitting of an atom's nucleus into two smaller nuclei and the release of two or three neutrons and energy

Question 39

when does induced nuclear fission occur

Answer 39

when a radioactive isotope (e.g. uranium 235) absorbs a neutron and the nucleus splits

Question 40

when does spontaneous fission occur

Answer 40

randomly, without a neutron being absobed.

Question 41

what is a chain reaction

Answer 41

when a fission event releases several neutrons, which causes other fissionable nuclei to split

Question 42

why is water a moderator in a nuclear reactor

Answer 42

it slows down fission neutrons

Question 43

what absorbs surplus neutrons to keep the chain reaction under control

Answer 43

control rods

Question 44

what is used to cool down fuel rods

Answer 44

water, it is a coolant

Question 45

the reactor core

Answer 45

a vessel made of thick steel to withstand high temperature and pressure. concrete walls to absorb ionising radiation

Question 46

what is nuclear fusion

Answer 46

the process of forcing the nuclei of two atoms close enough together so that they form a single larger nucleus

Question 47

how does nuclear fusion occur usually

Answer 47

two hydrogen nuclei fuse together under high temperatures and pressure to form a nucleus of a helium isotope.

Question 48

examples of nuclear fusion

Answer 48

the sun releases energy

Question 49

what is the by-product of nuclear fusion

Answer 49

energy

Question 50

simplest sun nuclear fusion

Answer 50

four hydrogen nuclei form one helium nuclei

Question 51

what are the difficulties of fusion reactors

Answer 51

-high temperatures and pressures to fuse nuclei, expensive -nuclei are hard to contain

Question 52

why are fusion reactors good?

Answer 52

-fuel is readily available, heavy hydrogen is in sea water -reaction product helium is non-radioactive, harmless -energy released could be used to generate electricity.

Question 53

which is better? fission or fusion

Answer 53

fusion!! no nuclear waste, easy resources (not uranium)

Question 54

example of problems with nuclear

Answer 54

chernobyl