Radioactivity

Question 1

What is radioactive decay?

Answer 1

When an isotope has an unstable nucleus it gives out radiation to become stable.

Question 2

What is the activity?

Answer 2

The rate at which a source of unstable neclei decay (measured in Bq)

Question 3

What can you use to measure the activity of a radioactive source?

Answer 3

A Geiger-Muller tube, by looking at the count rate (number f decays recorded each second by a detector

Question 4

What are the types of radiation given out by a nucleus?

Answer 4

Alpha, Beta, Gamma, Neutron

Question 5

What is an alpha particle the same as?

Answer 5

A helium atom

Question 6

What is a beta particle?

Answer 6

An electron which is ejected from the nucleus at a high speed

Question 7

Where do beta particles come from?

Answer 7

The nucleus- when a neutron changes into a proton and an electron.

Question 8

What is a gamma ray?

Answer 8

A type of electromagnetic radiation from the nucleus.

Question 9

What is an alpha particles range in air?

Answer 9

Alpha particles are large and can travel around 5cm in the air before colliding with air particles and stopping.

Question 10

What is the range of a beta particle in air

Answer 10

Beta particles can travel further than alpha particles. About 15cm before stopping.

Question 11

What is the range of gamma radiation in air?

Answer 11

Gamma radiation travels several metres in air before stopping, therefore has the greatest range in air.

Question 12

What is the penetrating power of alpha particles?

Answer 12

Alpha particles are stopped by a single sheet of paper.

Question 13

What is the penetrating power of beta particles?

Answer 13

Beta particles are stopped by a few mm of aluminium

Question 14

What is the penetrating power of gamma?

Answer 14

Gamma radiation is the hardest to stop, and is stopped by several centimetres of lead.

Question 15

What is ionsing power?

Answer 15

When radiation collides with atoms tit can cause the atoms the lose electrons and form ions.

Question 16

What is the ionising power of alpha?

Answer 16

Very strongly ionising

Question 17

What is the ionising power of beta?

Answer 17

Quite strongly ionsing

Question 18

What is the ionising power of gamma?

Answer 18

Weakly ionising.

Question 19

During alpha decay the atomic number…..

Answer 19

The atomic number decreases by 2

Question 20

During alpha decay the mass number…..

Answer 20

The mass number decreases by 4

Question 21

During beta decay the atomic number…

Answer 21

The atomic number increases by 1

Question 22

During beta decay the mass number…

Answer 22

The mass number remains the same!!!

Question 23

During gamma decay the atomic number and the mass number…

Answer 23

During gamma decay the atomic number and the mass number are not changed at all.

Question 24

Scientists cannot ….. radiative decay as it is a …… process

Answer 24

Scientists cannot predict when a nucleus will decay . Decay is a random process.

Question 25

What is half life?

Answer 25

The time it takes for the number of nuclei of the isotop in a sample to halve. OR the time it takes for the count rate from a sample containing the isotope to fall to half its initial level.

Question 26

How do you work out the half life using a graph?

Answer 26

Find half of the "number of undecayed nuclei" and find the time taken for this to happen.

Question 27

How do you calculate the decrease in count rate after a specific number of half lives?

Answer 27

Work out how many times the count rate would have "halved" or how many half lives go into the amount of time given.

Question 28

A radioactive isotope has a half life of 15 days and an initial count-rate of 200 counts per second. Determine the count rate after 45 days

Answer 28

Count rate = 200 15 days = half 200 (100) 30 days= half 100(50) 45 days= half 50 (25)

Question 29

What is the risk to ionising radiation?

Answer 29

It can increase the risk of cancer in humans.

Question 30

What is irradiation?

Answer 30

Irradiation is exposing an object to nuclear radiation

Question 31

Give a use for radiation in hospitals

Answer 31

Gamma is used for sterilisation for example a syringe.

Question 32

What do people who work with radioactive isotopes have to do?

Answer 32

Take precautions e.g. shielding, either gloves or a lead apron or monitoring by measuring how much radiation has been received (if too much we can stop them working with radioactive isotopes)

Question 33

What is radioactive contamination?

Answer 33

When unwanted radioactive isotopes end up on other materials

Question 34

Why is radioactive contamination hazardous?

Answer 34

As the radioactive atoms decay and emit ionising radiation.

Question 35

Which radiation is most dangerous to humans?

Answer 35

Alpha is strongly ionising but stopped by dead cells on the skin surface so is only dangerous if inhaled or swallowed therefore beta is more hazardous as it is quite ionising and can penetrate the skin into the body. Gamma is weakly ionising therefore when it penetrates the body it is likely to pass straight through.

Question 36

Why is it important that studies are published and shared with other scientists?

Answer 36

As the findings can be checked (peer review)