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Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What is radioactive decay?

A

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

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2
Q

What is the activity?

A

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

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3
Q

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

A

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

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4
Q

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

A

Alpha, Beta, Gamma, Neutron

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5
Q

What is an alpha particle the same as?

A

A helium atom

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6
Q

What is a beta particle?

A

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

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7
Q

Where do beta particles come from?

A

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

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8
Q

What is a gamma ray?

A

A type of electromagnetic radiation from the nucleus.

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9
Q

What is an alpha particles range in air?

A

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

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10
Q

What is the range of a beta particle in air

A

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

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11
Q

What is the range of gamma radiation in air?

A

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

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12
Q

What is the penetrating power of alpha particles?

A

Alpha particles are stopped by a single sheet of paper.

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13
Q

What is the penetrating power of beta particles?

A

Beta particles are stopped by a few mm of aluminium

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14
Q

What is the penetrating power of gamma?

A

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

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15
Q

What is ionsing power?

A

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

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16
Q

What is the ionising power of alpha?

A

Very strongly ionising

17
Q

What is the ionising power of beta?

A

Quite strongly ionsing

18
Q

What is the ionising power of gamma?

A

Weakly ionising.

19
Q

During alpha decay the atomic number…..

A

The atomic number decreases by 2

20
Q

During alpha decay the mass number…..

A

The mass number decreases by 4

21
Q

During beta decay the atomic number…

A

The atomic number increases by 1

22
Q

During beta decay the mass number…

A

The mass number remains the same!!!

23
Q

During gamma decay the atomic number and the mass number…

A

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

24
Q

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

A

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

25
Q

What is half life?

A

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.

26
Q

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

A

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

27
Q

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

A

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

28
Q

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

A

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

29
Q

What is the risk to ionising radiation?

A

It can increase the risk of cancer in humans.

30
Q

What is irradiation?

A

Irradiation is exposing an object to nuclear radiation

31
Q

Give a use for radiation in hospitals

A

Gamma is used for sterilisation for example a syringe.

32
Q

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

A

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)

33
Q

What is radioactive contamination?

A

When unwanted radioactive isotopes end up on other materials

34
Q

Why is radioactive contamination hazardous?

A

As the radioactive atoms decay and emit ionising radiation.

35
Q

Which radiation is most dangerous to humans?

A

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.

36
Q

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

A

As the findings can be checked (peer review)

Physics (24 decks)

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