Class resources

 
Derivation of Resistivity formula:
 
p = RA/L          R prop L       R prop 1/A       R prop R/A
 
R = p(L/A)       R = pL/A       p = RA / L.
 
 
Proof of monochromatic light formula
 
 
Proof of F = qVB
 
The Wheatstone bridge explained:
 
Why is ionising radiation considered dangerous?
The radiations from radioactive materials – alpha, beta and gamma radiation – are all ionising radiations which can damage living cells. Ionising radiation can break molecules into smaller fragments. ... This may result in the living cells dying or becoming cancerous. Radiation can also affect DNA, causing mutations.
When atoms in living cells become ionized one of three things usually happen – the cell dies, the cell repairs itself, or the cell mutates incorrectly and can become cancerous. Not all cells are affected by ionizing radiation in the same way.
If the radioactive source is outside the body: alpha radiation is not as dangerousbecause it is unlikely to reach living cells inside the body. beta and gamma radiationare the most dangerous sources because they can penetrate the skin and damage the cells inside.
 
 
Explanation of harmonics in pipes: