Physcs (P2) - Radioactivity

HideShow resource information
  • Created by: Roma
  • Created on: 14-12-13 11:23
What is radioactive decay?
When the nuclei of radioactive substances becomes stable. In this process they emit radiation and turn into other elements.
1 of 30
What are the three types of radiation emitted?
Alpha, beta and gamma radiation.
2 of 30
When will an unstable nucleus decay?
We don't know - it is a random process.
3 of 30
What is background radiation?
Radiation that is around us all the time. It is from radioactive substances in the environment, from space, from devices such as x ray tubes.
4 of 30
What did scientist used to think atoms were?
They thought they consisted of positively charged spheres with electrons stuck in them. This is known as the plum pudding model of the atom.
5 of 30
Who were Rutherford, Geiger and Marsden?
Scientists who devised an alpha particle scattering experiment, in which they fired alpha particles at thin gold foil.
6 of 30
What happened to most of the alpha particles in the experiment?
Most particles passed straight through the foil, meaning that the atom is just empty space.
7 of 30
What happened to some of the particles?
Some particles were deflected suggesting that the nucleus has a positive charge. A few rebounded through very large angles, suggesting that the nucleus has a large mass and a very large positive charge.
8 of 30
What happens during alpha decay?
The nucleus of the element loses 2 neutrons and 2 neutrons. The 2 protons and 2 neutrons are emitted as an alpha particle.
9 of 30
What happens during beta decay?
A neutron in the nucleus of the element changes into a proton and and electron. The electron created in the nucleus is instantly emitted.
10 of 30
What happens if an atom gains or loses an electron?
It becomes an ion.
11 of 30
What is an isotope?
A form of an element where atoms have the same number of protons but different number of neutrons.
12 of 30
What is the mass number?
The total number of protons and neutrons in an atom.
13 of 30
What is the atomic number?
The number of protons in an atom.
14 of 30
What is a beta particle?
A high speed electron from the nucleus.
15 of 30
What is gamma radiation?
An electromagnetic wave released from the nucleus. It has no charge and no mass as there is no change in the atomic number of the mass number.
16 of 30
What is ionisation?
When nuclear radiation travels through a material it collides with the atoms of the material. This knocks electrons off them creating ions. Ionisation in a living cell can damage or kill the cell.
17 of 30
How ionising are alpha particles?
They are relatively large, so have lots of collisions with atoms - they are strongly ionising.
18 of 30
How far can alpha particles penetrate?
They do not penetrate far into materials. They can be stopped by paper, skin or a few cm of air. They have a positive charge and are deflected by electric and magnetic fields.
19 of 30
How ionising are beta particles?
They are quite small and so are less ionising than alpha particles.
20 of 30
How far can beta particles penetrate?
They can penetrate further than alpha particles. They are stopped by a few cm of air or a sheet of aluminium. They have a negative charge and are deflected by electric and magnetic waves in the opposite direction to alpha particles.
21 of 30
How ionising are gamma particles?
They are electromagnetic waves so will travel a long way before colliding with other particles. This makes them weak ionisers.
22 of 30
How far can gamma particles penetrate?
They are very penetrating. A few cm of lead of several cm of concrete are needed to absorb most of the radiation. They are not deflected by magnetic of electric fields.
23 of 30
What is half life?
The average time it takes for the number of nuclei in a radioactive isotope to halve.
24 of 30
What is the activity of a radioactive source?
The number of nuclei that decay per second.
25 of 30
By how much do the number of atoms and activity both decrease?
The number of atoms of a radioactive isotope and the activity both decrease by half every half life.
26 of 30
What are alpha sources used for?
As smoke alarms. They are not dangerous because they are poorly penetrating. The source needs a half life of several years.
27 of 30
What are beta sources used for?
For thickness monitoring e.g. for paper and foil. The source needs a half life of many years, so that decreases in count are due to changes in the thickness of paper etc.
28 of 30
What are gamma and beta sources used for?
As tracers in medicine. The source is injected or swallowed by the patient and is monitored by a detector outside the patient. The source needs a half life so the patient is not exposed to large amounts of radioactivity.
29 of 30
What is radioactive dating used for?
To find the age of ancient material.
30 of 30

Other cards in this set

Card 2

Front

What are the three types of radiation emitted?

Back

Alpha, beta and gamma radiation.

Card 3

Front

When will an unstable nucleus decay?

Back

Preview of the front of card 3

Card 4

Front

What is background radiation?

Back

Preview of the front of card 4

Card 5

Front

What did scientist used to think atoms were?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Radioactivity resources »