Physic Additional Radioactive Stuff

Question 1

How was the atomic structure discovered?

Answer 1

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

Question 2

Describe the plum pudding model

Answer 2

The positive charged matter in the atom was spread out

And the electrons were buried inside

Question 3

What is the mass of a proton?

Answer 3

1

Question 4

What is the mass of a neutron?

Answer 4

1

Question 5

What is the mass of an electron?

Answer 5

1/2000

Question 6

What are isotopes?

Answer 6

Different forms of the same element

Question 7

What do isotopes have?

Answer 7

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

Question 8

What are the sources of radiation?

Answer 8

Space, cosmic rays from the sun
Air, food, building materials, rocks
Man made sources such as nuclear plants, wastes and disaster bombs

Question 9

Describe the alpha particle

Answer 9

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

Question 10

Describe beta particles

Answer 10

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

Question 11

Describe gamma radiation

Answer 11

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

Question 12

What does the damage depend on

Answer 12

Type and amount of radiation you have been exposed to

Higher the radiation risk the more at risk you are at developing cancer

Question 13

What does the radiation dose depend on

Answer 13

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

Question 14

What happens when alpha and beta particles go through a magnetic field?

Answer 14

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

Question 15

What happens to gamma radiation when it goes through a field?

Answer 15

It has no charge so it doesn’t get deflected

Question 16

What is a half life?

Answer 16

The average time it takes for the number of nuclei in a isotope to halve

Question 17

What is a short half life?

Answer 17

Activity falls quickly because lots of nuclei decay quickly

Question 18

What is a long half life?

Answer 18

Activity falls more slowly because the nuclei doesn’t decay for a long time

Question 19

How do smoke detectors work?

Answer 19

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

Question 20

How do radioactive travers work?

Answer 20

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

Question 21

What is radiotherapy?

Answer 21

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

Question 22

What does ionisation do?

Answer 22

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

Question 23

What is nuclear fussion?

Answer 23

The splitting up of atomic nuclei

Question 24

How does nuclear fission work?

Answer 24

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

Question 25

What are the advantages and disadvantages of nuclear fission?

Answer 25

• disposal of nuclear waste as the products left over are radioactive so cant just be thrown away, it is difficult and expensive to dispose of safely
• chernobyl
• overall cost of running is high due to the cosy of the power plant and final decommissioning
  + nuclear fuel is cheap

Question 26

How does a nuclear power station work?

Answer 26

In a nuclear reactor the atomic nuclei split up and release heat energy in a controlled chain reaction
This heat heats water to make steam which drives a steam turbine which makes electricity from a generator
Control rods absorb surplus neutrons to keep the chain of reaction controlled
Made of thick steel to with stand high temperatures and pressures
Water acts as a coolant

Question 27

What is nuclear fusion?

Answer 27

The joining of small atomic nuclei

Question 28

What are the advantages and disadvantages of nuclear fusion?

Answer 28

+ releases more energy than fission
+ doesn’t leave behind a lot of waste like fission
- only happens at really high temperatures
- need an extremely strong magnetic field to hold the reaction

Question 29

How doe nuclear fusion work?

Answer 29

When 2 protons fuse together they form a heavy hydrogen nucleus
Then 2 more protons collide separately with two heavy hydrogen nuclei and turn them in to a heavier nuclei
The 2 heavier nuclei collide to form the helium nucleus
Energy Released at each stage is carried away as kinetic energy of the product nucleus

Question 30

Describe the life cycle of a star

Answer 30

Stars initially form from clouds of dust and gas, the forces of gravity make the gas and clouds come together to form a protostar
Gravitational energy is converted into heat energy and the temperature rises, when it is hot enough the hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out heat and light
Smaller masses of dust and cloud join together and form planted which orbit the star
The star balances the force, the heat created by nuclear fusion pushes outwards and the force of gravity pushing everything inwards this is called the main sequence star eventually the hydrogen runs out and the nuclear fusion of helium makes heavier elements such as iron
Star swells out to a red giant or red super giant
If it is a red super giant = it undergoes more fusion and expands, then it forms elements heavier than iron in a supernova, and it forms plants and stars, then it goes to a neutron star and if its big enough a black hole
If it is a red giant it goes to a white drawf and then cools to a black drawf