Radioactivity
who came up eith the first idea of an atom
John Dalton
What was JJ Thompsons theory of the atom
Electrons were seperate. atoms are spheres of positive charge
Who were the three scientists who conducted the gold scattering experiment?
Rutherford. Marsden and Geiger
What did Ritherford deduce when most alpha particles passed through the gold foil?
The atom was mostly empty space
What was deduced by some alpha particles being deflected ar large angles?
All the mass was in the centre of the atom
Why was it essential that the apparatus was jn an ecacuated chamber in scattering experiment?
so no other particles would interfere
Why was it essential the foil was thin in scattering experiment?
If it was thick, many more particles would have been deflected
Why was it essential all alpha particles had the same speed in scatterimg experiment?
If they had different speeds they would deflect different amounts
Why was it essential the beam was narrow in the scattering experiment?
You would always get some alpha particles being deflected
What is the nature, charge, ionising ability, pentrating ability and uses of an Alpha particle?
Helium nucleus, 2 , high, low (paper), smoke detector
What is the nature, charge, ionising ability, pentrating ability and uses of a Beta particle
High soeed electron, -1, Medium, Medium (Alumminium), Cancer/medical
What is the nature, charge, ionising ability, pentrating ability and uses of a gamma ray
Electromagnetic radiation, 0, Low, high (lead), radiotherapy
List 6 sources of background radiation
Radom gas
Rocks and buildings
Cosmic rays
Food and drink
Medical
Radioactive fallout (chernobyl)
Why are gamma rays used in medicine
Low ionistion rate
Explain how a gamma emitter is used as a tracer in medicine
A gamma emitter can diagnose a problem without surgery
A source with short half life is injected into body
What is a gamma beam and how is damage minimised
Intense radiation on tumor site
Rotating beam
List side effects of gamma radiation in medicine and how are medical staff protected
Tiredness
Red skin due to death of healthy cells
Exposure minimised
Room has lead lined walls
Explain what the most common isotope used and and why
Technetium 99m.
Hakf life is 6 hours
Gamma emitter
Can be attached to pharma ceautical thay transports to select location
What are the points of the line of stability?
(10,10) (20,20) (40,60) (60,92) (80,120)
When does electron capture take place and what is released
Happens in proton rich nuclei, and electron neautrino released with a gamma photon
What are the two methods too find the radius of a nuclei
Alpha particle scattering and Electron diffraction
what is the definition of an electron volt
When an electron is accelerated through 1V it gains Ek equal to 1ev
What is the angle of the first minima produced?
sinx = 0.61(lamda) / R
r is the radius of thr nucleus