whta do you measure radioactivity with?
Whaty makes an atom radioactive?
-this is when the nucleus is unstable
-decays to become more stable
-emits energetic radiation
what are the three types of radiation and what are their properties?
alpha- goes a few centemeters in air, very penetrating
beta- less penetrating, goes 10-15 centemeters in air
gamma rays- most penetrating radiation, penetrates many meters
What did scientists know about atom's structure before?
- thought the atom was a solar system model
Describe Rutherford's experiment?
- Start with a metal foil. Use gold, because it can be rolled out very thin, to a thicknedd of just a few atoms.
- Direct a source of alpha radiation at the foil. Do this in a vacuum chamber, so that the alpha particles are not absorbed by the air
- Watch for flashes of light as the alpha particles strike the detecting material on the screen at the end of the microscope
- Work all night, counting the flashes at different angles, to see how much alpha radiation is detected.
What were Rutherfords observations?
- most particles went straight through
-a few deflect by a few degrees
- small fraction completly deflected
What was the reason for Rutherfords oberservations?
-the nucleus is positive
- reason for deflecting radiation
What is an isotope?
- an isotope is a different type of an a element
e.g. carbon six proton
-can have different number od neutrons
How to nuclear equations work?
What are some specific details about alpha particles?
- haevier than beta particles
- collide quickly with air molecules and slow down
- gain electrons to become helium atoms
- ionising but not penetrating
what are specific details about beta radiation?
=- fast moving electrons
- smaller than alpha, less likely to collide with air
- less ionising
- act like electrons when they slow down
What are some specific details about gamma radiation?
-released when a nucleus emits an alpha or beta particle and the atoms in the nucleus rearrange to a lower energy state
- does not change element
- very penetrating
- very weak ionising
What is a use of ionising radiation?
-Food irradiation- Gamma radiation
- kills bacteria
- sterilising medical equipment
- kills bacteria
medical produces- Cancer
- smoke alarm
- exit signs
- nuclear weapons
What are some sources of radiation?
What are radiation units and what is the reccomended dose in the Uk?
-mSv- milli- seaverts
- if someones with dose of 100-mSv
-three out of a hundred will develop cancer
- can be exposed to cosmic rays 0.1mSv
What can affect a radiation dose?
- tupe of particles e. g. alpha- 20 dose
gamma rays- 1 dose
- alpha paticles are only hazards in the body
- damage depends on effected area
- Radon gas. breathed in
-can cause damage
- dose is affected by
- time of exposure
-type of particles
- and amount body of material
Why ionising radiation dangerous?
- cause DNA molecules to behave abnormally
- Cells may form cancer
- one Radon atom can cause cancer
What is irradiation and what is the difference compared to contamination?
-exposure to radiation source to outside your body
Danger scale: 1.gamma 2. beta 3. alpha
- this when a source gets inside the body
Danger scale: 1.alpha 2. beta 3.gamma
What are some precautions to lower the radiation dose for radiation workers?
- use protective clothing and screens
- wear gloves +aprons
-wear special devices to moniter their dose
Who discovered Radon and how does it effect the body?
- discover by georgius agricola a doctor
- noticed high death rate of german silver miners
- thought it was duie to breathing in dust
- high concentration of Radon in mines
- radioactives -ionising
- causes lung cancer
How can radon build up its concentration?
- by being trapped in enclosed spaces
How many deaths a year does.......?
- with a population of 69 million in 2008
Describe graphs of radioactive activity and how to calculate the half-lfe?
-negative correlation between activity and time
- take a point high on the graph, they take half of it and on the activity axis. then subtract the t(1) from t(2)= half life
What is one use of gamma rays in medicine?
- contaminates patients
- have to flush toilet multiple times
- wash hans thouroughly
- avoid close contact
- benefits outweigh the risks
- gamma rays can cause damagine to healthy cells
What is an example of radiotherapy?
- thyroid cancer
- swallowed- goes to thyroid naturally
and kills cells through beta radiation
What is an example of nuclear fission?
-when uranium splits releases a huge amount of energy
- can be calculated by E=mc(2)
- reaction controled by using rods of boron which absorb neutrons
What is a by product of nuclear fission?
- Plutonium can be used to make nuclear weapons
How are nucleuses held together?
- strong nuclear force
- atoms are at exactly the right distance apart
-it is a balanced by electriacal force
What si nuclear fusion?
-isotopes repel eachother due to electrical force
- if they get close enough the attractive force brings them together
- takes a lot of energy to do this
- energy released- can be calculated by E=mc(2)
-products of the reaction
why is fusion better than fission?
-less nuclear waste
- more fuel(water)