AQA Combined Physics 6.4

Question 1

What does a short half-life mean?

Answer 1

The activity falls quickly due to rapid decay

Question 2

What is half-life?

Answer 2

The time taken for the number of nuclei of a radioactive isotope to halve

Question 3

Why is radioactive contamination so dangerous?

Answer 3

Radioactive particles could get inside the body

Question 4

What is the hazard of radioactive contamination?

Answer 4

The hazard is due to the decay of the contaminating atoms

Question 5

How can net decline be calculated?

Answer 5

1) Find the activity after each half-life
2) Divide the final activity by the inital
3) Multiply by 100 to make a percentage

Question 6

How can the process of radioactivity be described?

Answer 6

Random

Question 7

What would be the nuclear equation for the decay of Uranium-238

Answer 7

238 U - 234 Th + 4 He

92 90 2

Question 8

How many protons does an atom of the same element have?

Answer 8

The same number

Question 9

How can electron arrangements change?

Answer 9

• Absorption of electromagnetic radiation (higher energy level)
• Emission of electromagnetic radiation (lower energy level)

Question 10

Describe the basic structure of an atom

Answer 10

A positively charged nucleus orbited by negatively charged electrons

Question 11

How did Bohr adapt the nuclear model as suggested by Rutherford?

Answer 11

Bohr suggested electron orbit the nucleus at specific distances (energy levels)

Question 12

What was the Plum Pudding model?

Answer 12

The atom was suggested to be a ball of positive charge with negative electrons embedded in it

Question 13

What did Rutherford’s scattering experiment show?

Answer 13

The mass of the atom was concentrated in the centre (nucleus) and it was charged

Question 14

Before the discovery of the electron, what were atoms thought to be (as suggested by Dalton)?

Answer 14

Tiny spheres that could not be divided

Question 15

Describe alpha radiation (structure, penetration, absorption and ionising strength)

Answer 15

• 2 neutrons and 2 protons (like a helium nucleus)
• They don’t penetrate very far (a few cm in air)
• Are absorbed by a piece of paper
• They are strongly ionising

Question 16

What can a Geiger-Muller tube record?

Answer 16

The count-rate (number of radiation decays reaching the device per second)

Question 17

What is ‘activity’ in terms of nuclear radiation?

Answer 17

The rate at which a source of unstable nuclei decays

Question 18

20 years after the nucleus became scientifically accepted, what did James Chadwick identify?

Answer 18

Neutrons

Question 19

What can nuclear radiation emission change in a nucleus?

Answer 19

The mass or the charge

Question 20

What happens to the radioactivity of a source over time?

Answer 20

It decreases

Question 21

How can an alpha particle be represented?

Answer 21

4
He
2

Question 22

How is nuclear ‘activity’ measured?

Answer 22

In becquerels (Bq) where 1 Bq is 1 decay per second

Question 23

What happens to Rn^219^ when it experiences alpha decay?

Answer 23

219 215 4
radon —– polonium + He
86 84 2
*Mass and charge both decreased

Question 24

How can a beta particle be represented?

Answer 24

0
e
-1

Question 25

What can nuclear equations represent?

Answer 25

Radioactive decay

Question 26

Describe gamma radiation (structure, penetration, absorption and ionising strength)

Answer 26

- Waves of electromagnetic radiation - Penetrate far into materials - Absorbed by thick sheets of lead or metres of concrete - Weakly ionising

Question 27

As well as alpha, beta and gamma radiation what else can radioactive substances release?

Answer 27

Radioactive substances can release neutrons (as they rebalance their atomic and mass numbers)

Question 28

Some atomic nuclei are unstable - what can the nucleus emit (and in doing so become more stable)?

Answer 28

Radiation - a random process of radioactivity decay or the unstable nuclei

Question 29

What is radioactive contamination?

Answer 29

The unwanted presence of materials containing radioactive atoms on other materials

Question 30

What happens to the mass or charge of a nucleus when it experiences gamma emission?

Answer 30

The mass and charge remain the same

Question 31

What happens to C^14^ when it experiences beta decay?

Answer 31

14 14 0 carbon ---- nitrogen + e 6 7 -1 *Mass remains but charge increased

Question 32

Describe beta radiation (structure, penetration, absorption and ionising strength)

Answer 32

- A fast moving electron (virtually no mass) - Penetrate a few metres in air - Are absorbed by a 5mm sheet of aluminium - Moderatley ionising

Question 33

Approximately how big is the radius of an atom?

Answer 33

Very small - a radius of about 1x10^-10^m

Question 34

What does a long half-life mean?

Answer 34

The activity falls slowly due to slow decay?

Question 35

Inside the body what radioactivity source is most dangerous?

Answer 35

Alpha

Question 36

What is the overall electrical charge of an atom?

Answer 36

No overall charge - electron and proton numbers are equal

Question 37

What is the atomic number?

Answer 37

The number of protons in an atom

Question 38

How much smaller is the radius of a nucleus compared with the radius of an atom?

Answer 38

1/10,000th the radius of an atom (but contains most of the mass)

Question 39

How are electron arranged around the nucleus of an atom?

Answer 39

Electrons are arranged at different distances from the nucleus

Question 40

What happens to an atom if it loses one or more outer electron(s)

Answer 40

It becomes a positive ion

Question 41

What is an isotope?

Answer 41

Atoms of the same element with different numbers of neutrons

Question 42

What types of ionising nuclear radiation are there?

Answer 42

1) Alpha 2) Beta 3) Gamma

Question 43

What is irradiation?

Answer 43

Exposing an object to nuclear radiation (the object itself does not become radioactive)

Question 44

Outside of the body what radioactive sources are most dangerous?

Answer 44

Beta and Gamma

Question 45

What can the positive charge of a nucleus be subdivided into?

Answer 45

Protons

Question 46

What is the mass number?

Answer 46

The number of protons and neutrons in an atom

Question 47

What precautions should be taken around hazardous radioactive materials?

Answer 47

- Wearing gloves / using tongs - Protective suits - Breathing apparatus - Limiting exposure time