Chapter 24 Particle Physics Flashcards
What was the plum pudding model?
Electrons were contained in a sea of positive charge
What happened in Rutherfords alpha scattering experiment?
Alpha particles were fired at a thin metal foil
The alpha particles were deflected
Measurements were taken to see the angle at which the particles were deflected and how many were deflected
What observations were made during the experiment?
Very few alpha particles were scattered and most went straight through
Very very few particles were deflected through angles more than 90*
What conclusions were drawn from the experiment?
Most of the nucleus of an atom is empty space (because most past through)
The nucleus had a positive charge because it repelled some alpha particles
How did rutherford calculate the size of the nucleus?
He worked out that when an alpha particle is fired with energy towards the nucleus it will momentarily stop before being repelled away. If you know the kinetic energy of the alpha particle then u know how close it got to the atom. Using this you get an upper limit of the size of the nucleus. This is the distance of closes aproach
What is the equation for the radius of a nucleus?
R = r0 x A^1/3
r0 = 1.2x10^-15 A = Number of nucleuons (protons / Neutrons)
Atoms would seem to completely fall apart because the protons repel each other so strongly and gravity is too weak to hold them together. What is?
The strong nuclear force
What are the properties of the strong nuclear force?
Attractive to about 3fm
Repulsive below 0.5fm
What is antimatter?
It is the opposite of matter. Has the same mass but has the opposite charge
What are the 4 fundamental forces?
Strong Nuclear
Weak Nuclear
Electromagnetic
Gravitational
What does weak nuclear force do?
It causes beta decay
What conditions need to be met for gravitational force?
The object / Particle needs to have mass
What conditions need to be met for electromagnetic force?
The object / particle needs to have a charge
What is a hadron? examples
Particles / antiparticles that are affected by the strong nuclear force
protons, neutrons, maesons
What are leptons? and examples?
They are particles and antiparticles that are not affected by the strong nuclear force
electrons, neutrinos, muons