Physics 2.6

Physics 2.6

1. A radioactive substance contains unstable nuclei that become stable by emitting radiation

   • Alpha, beta and gamma radiation
   • Radioactive decay cannot be predicted
   • The origins of background radiation are: air (radon), medical (x-rays), the ground (rocks), food and drink, cosmic rays from space, nuclear weapons, air travel and nuclear reactors

2. Rutherford used measurements from alpha scattering experiments to prove that atoms have small + charged nuclei where most of the mass is located

   • 'Plum pudding model' couldn't explain why some alpha particles were scattered through large angles
   • The nuclear model of the atom explains why alpha particles are scattered

3. Isotopes of an element are atoms with same number of protons but different number of neutrons - same atomic number but different mass number

4. A magnetic or electric field can separate a beam of alpha, beta and gamma

   • They ionise substances they pass through, ionisation can kill or damage cells

5. The half life of radioactive isotopes is the average time taken for the number of nuclei in a sample to halve

   • The activity of a radioactive source is the number of nuclei that decay per sec

6. The use of a radioactive isotope depends on:

   • 1) its half life
   • 2) type of radiation given out
   • For monitoring, isotope needs a long half life
   • Tracers should be beta or gamma which last long enough to monitor but not too long
   • For radio active dating of a sample an isotope with a similar half life needs to be used

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