Radiation & half-life

Question 1

What is radioactivity?

Answer 1

Some atomic isotopes are unsafe and emit radiation to become more stable.

Question 2

What is an alpha particle?

Answer 2

A particle with 2 neuron’s and 2 proton’s.

Question 3

What is the electric charge of an alpha particle?

Answer 3

+2

Question 4

What is the relative atomic mass of an alpha particle?

Answer 4

4

Question 5

What is the penetrating power of an alpha particle?

Answer 5

It is stopped by paper or a few cm of air.

Question 6

What is the ionising affect of an alpha particle?

Answer 6

Strongly ionising.

Question 7

What is the effect of the magnetic/electrical field of an alpha particle?

Answer 7

It is weakly deflected.

Question 8

What is a beta particle?

Answer 8

A high energy electron.

Question 9

What is the electrical charge of a beta particle?

Answer 9

-1

Question 10

What is the relative atomic mass of a beta particle?

Answer 10

0 or 1/1836 that of the proton mass.

Question 11

What is the penetrating power of a beta particle?

Answer 11

Stopped by a few mm of aluminium.

Question 12

What is the ionising affect of a beta particle?

Answer 12

Weakly ionising.

Question 13

What is the effect of the magnetic/electric field of a beta particle?

Answer 13

Strongly deflected.

Question 14

What is a gamma ray?

Answer 14

High energy electromagnetic radiation.

Question 15

What is the electrical charge of a gamma ray?

Answer 15

0

Question 16

What is the relative atomic mass of a gamma ray?

Answer 16

0

Question 17

What is the penetrating power of a gamma ray?

Answer 17

Stopped by several cm of lead or several m of concrete.

Question 18

What is the ionising affect of a gamma ray?

Answer 18

Very weakly ionising.

Question 19

What is the effect of the magnetic/electric feild of a gamma ray?

Answer 19

Not deflected.

Question 20

What are alpha particles used in?

Answer 20

Radiotherapy.

Question 21

What are beta particles used in?

Answer 21

They’re used in bio markers and in PET scanners which use radioactive tracers to image blood flow and other metabolic processes.

Question 22

How are gamma rays used?

Answer 22

In x-rays to produce images.

Question 23

What is half life?

Answer 23

The time taken for the number of radioactive nuclei in an isotope to half.

The number of radioactive nuclei will decrease over time as they decay, causing them to become stable.

Question 24

How do you measure the rate of the decrease of radioactive nuclei in an isotope?

Answer 24

You can do this via the half life of a sample.

Question 25

Is half life affected by number of nuclei and external conditions?

Answer 25

No, it remains constant.

Question 26

How do you find half life graphically?

Answer 26

You can produce a graph showing the number of radioactive nuclei over tome.

Half life can be found from:
• The time taken for the number of radioactive nuclei to halve from the graph.

Question 27

What is the mass of a radioactive sample proportionate to?

Answer 27

The number of radioactive nuclei remaining.

This means we can find the half life from a graph showing the mass of a radioactive isotope remaining over time.

Question 28

What is the number of radioactive nuclei present proportionate to?

Answer 28

• The activity of a source.

Activity of Decay No. radioactive
a source = constant x nuclei present

Question 29

What is count rate proportionate to?

Answer 29

Activity of a source.