Nuclear Physics Flashcards
rutherford scattering
originally plum pudding model
studied scattering of alpha particles from a radioactive source producing a tiny flash of light when they pass the fluorescent screen
conclusions from Rutherford scattering
atom must be mostly empty space as alpha particles pass directly through it
the nucleus must be positively charged as some positive alpha particles deflected
the nucleus muscles be very tiny as few deflected at an angle larger than 90 degrees
most of the mass is within the nucleus as the fast alpha particles are deflected
properties of alpha beta and gamma rays
alpha- 2 protons & 2 neutrons, +2 charge, few cm in range, stopped by paper, high ionisation
beta- free electron, -1 charge, 10s cm in range, stopped by aluminium, medium ionisation
gamma ray- electromagnetic ray, 0 charge, infinite range, reduced by lead, low ionisation
ionisation
the process in which an electron is given enough energy to break away from an atom is called ionisation
background radiation
there is always low levels of background radiation
decay constant
the constant of proportionality- the probability of a specific nucleus decaying per unit of time
nuclear fission and fusion
fission- large nuclei that can randomly split into two smaller nuclei, energy is released
fusion- when 2 nuclei combine to create one larger nuclei, energy released due to heavier nuclei created
Changes in Atomic models
Thought particles where indivisible
Positive bodies with negative electrons in them
Rutherford then discovered that they were mostly empty space with electrons orbitting them
The Plum Pudding Model
Atoms were a ball of postive charge with negative electrons evenly distributed throughout them
Rutherford scattering
Alpha particles fired at thin gold foil- with plum pudding model, particles were expected to pass through
Actually …
Most passed through- suggesting atoms mostly empty space
Some were deflected at large angles sugessting that there is a positively charged nucleus that repels alpha particles
Few were deflected less than 90° suggesting that the nucleus was very dense
Alpha Radiation
2 protons
2 neutrons
Helium nucleus
Strongly ionising
Slow moving
Stopped by paper
Deflected in magnetic field
Beta Radiation
Electron
Positron
Mildly ionising
Fast moving
Stopped by aluminium
Negative charged
Deflected in magnetic field
Gamma Radiation
Electromagnetic radiation
High frequency
Weak ionising
Travels at speed of light
Stopped by lead
Chargeless
Uneffected by fields
How to safely handle radiation
Never directly handle source
Long- armed tongs
Sinage and warning lables
Minimum time handling
Store in lead box
Background Radiation
Radon gas
Rocks
Cosmic Radiation
Nuclear weapon testing
Nuclear disasters
