Radioactivity

Question 1

What is radioactivity?

Answer 1

the process by which an unstable nucleus becomes more stable

Question 2

Which sources significantly contribute to background radiation?

Answer 2

• radon gas in air
• rocks and buildings
• food and drink
• cosmic rays

Question 3

How can ionising nuclear radiation be measured?

Answer 3

using a detector connected to a counter

Question 4

A detector is connected to a counter to…

Answer 4

measure ionising nuclear radiation

Question 5

How is count rate measured?

Answer 5

counts/s or counts/minute

Question 6

How is the emission of radiation from a nucleus?

Answer 6

spontaneous and random in direction

Question 7

The _______ is spontaneous and random in direction.

Answer 7

emission of radiation from a nucleus

Question 8

What is an alpha particle?

Answer 8

helium nucleus

Question 9

What is an alpha particle’s ionising effects? Why?

Answer 9

highly ionising due to its large mass and charge

Question 10

What is an alpha particle’s penetrating abilities?

Answer 10

• least penetrating
• travel about 5 cm through air, stopped by materials such as thin paper or skin

Question 11

State the order of ionising effects of the three types of radiation.

Answer 11

1. alpha
2. beta
3. gamma

Question 12

What is a beta particle?

Answer 12

a high-energy electron

Question 13

What is a beta particle’s ionising effects? Why?

Answer 13

• mildly ionising
  -fast, large KE, although the mass is small
• charge of -1
• beta particles can still strip away electrons of other atoms they encounter

Question 14

What is a beta particle’s penetrating abilities?

Answer 14

can travel through skin, stopped by a few millimetres of aluminium

Question 15

What are gamma emissions?

Answer 15

high frequency electromagnetic waves

Question 16

What is gamma’s ionising effects? Why?

Answer 16

• weakly ionising
• they have no charge and no mass

Question 17

What is gamma’s penetrating abilities?

Answer 17

only stopped by several cm of lead (dense)

Question 18

Effect of a magnetic field on gamma

Answer 18

none

Question 19

Effect of a magnetic field INTO page on alpha

Answer 19

deflects slightly upwards

Question 20

Effect of a magnetic field OUT OF page on alpha

Answer 20

deflects slightly downwards

Question 21

Effect of a magnetic field INTO page on beta

Answer 21

deflects a lot downwards

Question 22

Effect of a magnetic field OUT OF page on beta

Answer 22

deflects a lot upwards

Question 23

Effect of an electric field on gamma

Answer 23

none

Question 24

Effect of an electric field on alpha

Answer 24

deflects towards negative side (less than beta)

Question 25

Effect of an electric field on beta

Answer 25

deflects towards positive side a lot

Question 26

Why do alpha only deflect slightly?

Answer 26

large mass compared to its charge

Question 27

Why do beta deflect a lot?

Answer 27

very small mass compared to its charge

Question 28

If a beta particle deflects upwards in a magnetic field, the field is....

Answer 28

out of the page

Question 29

If a beta particle deflects downwards in a magnetic field, the field is....

Answer 29

into the page

Question 30

If an alpha particle deflects upwards in a magnetic field, the field is....

Answer 30

into the page

Question 31

If an alpha particle deflects downwards in a magnetic field, the field is....

Answer 31

out of the page

Question 32

What is radioactive decay?

Answer 32

a change in an unstable nucleus that can result in the emission of alpha or beta and/or gamma

Question 33

What happens during alpha or beta decay?

Answer 33

the nucleus changes to that of a different element

Question 34

In what types of decay does the nucleus change to a different element?

Answer 34

alpha or beta decay

Question 35

Why may isotopes of an element be radioactive?

Answer 35

excess of neutrons in the nucleus/heavy nucleus

Question 36

What is the effect of alpha/beta decay and gamma emissions on the nucleus?

Answer 36

- increased stability - reduced number of excess neutrons

Question 37

What happens in beta emission?

Answer 37

neutron -> proton + electron - proton stays in the nucleus - electron is the beta particle

Question 38

What is the decay equation like for alpha decay?

Answer 38

forms helium nucleus, element loses 4 in nucleon number and 2 in atomic number

Question 39

What is the decay equation like for beta decay?

Answer 39

an electron is ejected and the element gains 1 in atomic number

Question 40

What is the decay equation like for gamma decay?

Answer 40

element stays the same in nucleon/proton number but becomes more stable

Question 41

Define the half-life of a particular isotope.

Answer 41

time taken for half the nuclei of that isotope in any sample to decay

Question 42

State some effects of ionising nuclear radiation on living things.

Answer 42

- cell death - mutations - cancer

Question 43

State some safety precautions for all ionising radiation.

Answer 43

- reducing exposure time - distance - using shielding to absorb radiation - do not point sources at people

Question 44

How should you store alpha?

Answer 44

- thin package as α-particles are weakly penetrating - protective clothing must still be worn when handling

Question 45

How should you store beta?

Answer 45

lead container

Question 46

How should you store gamma?

Answer 46

bury deep underground

Question 47

charge of alpha particles

Answer 47

+2

Question 48

State and describe one use of alpha particles

Answer 48

Smoke detectors - particles ionise the air and allow current to flow between positive and negative plates, with potential difference between them. when smoke is present, alpha particles collide with and are absorbed by smoke particles, so less current flows, causing the alarm to sound

Question 49

do gamma rays have mass and charge

Answer 49

nope nope nope

Question 50

state and describe a use of gamma rays

Answer 50

medical tracers - due to it being highly penetrating, it is easy to detect which areas of the body it has travelled. it is weakly ionising so it is not dangerous in small dose

Question 51

What is half life

Answer 51

Time taken for the count rate of a radioactive source to decrease by half