Physic Additional Radioactive Stuff Flashcards
How was the atomic structure discovered?
Rutherford and Marsden fired a beam of alpha particles at thin gold foil, they expected that the positively charged alpha particles would be deflected back by the negatively charged electrons
In fact most of the alpha particles went straight thorough and only a few got deflected back
So they realised
That most of the mass of the atom was concentrated at the centre in what they called a nucleus, and the nucleus had ti have a positive charge since it repelled the positive alpha particles at large angles more over most of the atom was empty space
Describe the plum pudding model
The positive charged matter in the atom was spread out
And the electrons were buried inside
What is the mass of a proton?
1
What is the mass of a neutron?
1
What is the mass of an electron?
1/2000
What are isotopes?
Different forms of the same element
What do isotopes have?
The same number of protons but a different number of neutrons
The same atomic number but different mass numbers
Some are radioactive and decay into other elements giving out radiation
What are the sources of radiation?
Space, cosmic rays from the sun
Air, food, building materials, rocks
Man made sources such as nuclear plants, wastes and disaster bombs
Describe the alpha particle
Helium nuclei 2 neutrons and 2 protons Big heavy slow moving Don't penetrate far into the material and are stopped quickly Short range in air Strongly ionising, bump into aims and knock electrons of them A-4. 4 Z-2 2
Describe beta particles
Electrons Quite fast and small Penetrate moderately into materials before colliding Long range in air Moderately ionising For every beta particle emitted a neutron turns into a proton A. 0 Z+1. -1
Describe gamma radiation
Short wavelength and electromagnetic waves
Penetrate far into materials without being stopped
Lass straight through air
Weakly ionising as they don’t collide with atoms
No mass or charge
What does the damage depend on
Type and amount of radiation you have been exposed to
Higher the radiation risk the more at risk you are at developing cancer
What does the radiation dose depend on
Underground rocks can cause higher levels on the surface - miners
Nuclear industry they are exposed to more radiation so they wear special clothing and have film badges
Radiographers in hospitals wear lead aprons and stand behind lead screens
High altitudes, closer to cosmic rays
What happens when alpha and beta particles go through a magnetic field?
When travelling through a magnetic field they will both be deflected but in opposite directions because of there opposite charges
Alpha particles have a larger charge than beta particles so they will feel a grater force from a magnet and electric field but they are deflected less because they have a greater mass
What happens to gamma radiation when it goes through a field?
It has no charge so it doesn’t get deflected
What is a half life?
The average time it takes for the number of nuclei in a isotope to halve
What is a short half life?
Activity falls quickly because lots of nuclei decay quickly
What is a long half life?
Activity falls more slowly because the nuclei doesn’t decay for a long time
How do smoke detectors work?
Alpha cause ionisation and therefore a current flows between the 2 electrodes, if there is a fire the smoke will absorb the radiation and the current will stop so an alarm will sound
How do radioactive travers work?
Have to be short half life of beta and gamma this is because they are less ionising and pass quickly out of the body and should only last a few hours
It is injected or swallowed and there progress around the body is followed using an external detector this converts reading to a display showing where the strongest reading is coming from
What is radiotherapy?
High dosages of gamma will kill off all living cells including cancerous cells, if it is directed carefully at just the right dosage it can kill the cancer cells without damaging too many normal cells
What does ionisation do?
Enter the cells and collide with molecules which causes ionisation this damages and destroys molecules
It can cause mutant cells which divide uncontrollably this is called cancer
What is nuclear fussion?
The splitting up of atomic nuclei
How does nuclear fission work?
A slow moving neutron must be absorbed into uranium or plutonium nucleus this makes the nucleus unstable causing it to split
Each time the uranium or plutonium splits it spits out 2 or 3 neutrons, one of these may hit another nucleus causing it also to split this keeps the chain reaction going
This gives out a lot more energy than you get from chemical reactions
