Nuclear Physics Flashcards
what is Rutherfords scattering experiment?
firing alpha particles at a piece of gold foil, surrounded by a fluorescent screen
- if alpha particles stuck it would glow green
- it was done in a vacuum
what were the 3 conclusions form the scattering experiment?
- most of the atom is empty space
- most of the mass is contained in once space (nucleus)
- (nucleus) mass is positively charged
what is the closest approach
firing an alpha particle at a nucleus, the particle repels, kinetic energy turns into potential. so where v=0, gives an overestimate of the radius
what is the closest approach equation
initial Ek= 1/4 πε*Qq/r
what are the disadvantages of the closest approach method
- its an overestimate
- needs thin samples
- needs mono energetic beams
- affected by SNF at close ranges
what is the electron diffraction method for measuring radii
firing electrons at foil to create a diffraction pattern. So you can measure the interference pattern
what is the electron diffraction equation for measuring radii
sinθ=1.22λ /d
what are advantages and disadvantages for electron diffraction
advantages
-electrons aren’t affect by SNF
disadvantages
-need very high speeds for wavelength to be same order of magnitude as diameter
-first minima difficult to detect
-needs mono energetic beams
what’s the relationship between nucleons and radius
not linear adding 1 nucleon to 4 significantly increases it but adding 1 nucleon to 225 doesn’t
how can you make the relationship linear
radius is directly proportional to the cube root of the nucleon number
what’s the nuclear radius equation
r=r0*A^1/3
what is the number of r0
1.4x10^-15(1.4fm)
calculating nuclear density
nuclear density is aways the same , as if you have 2 balls of the same material, regardless of size, they will always have the same density
atomic density vs nuclear density
nuclear- 10^17
atomic-10^3
What are the properties of alpha radiation
-Helium nucleus
- relative charge +2
-relative mass +4
- range in air 3-5cm
-blocked by paper
what are the properties of beta minus radiation
- electron
-relative charge -1
-relative mass 1/2000
-range in air 1-2m
-blocked by aluminium foil
what are the properties of beta plus radiation
- positron
-relative charge +1
-relative mass 1/2000
-Range in air 0m - blocked by electron (annihilation)
what are the properties of gamma radiation
- EM wave
-relative charge 0
-relative mass 0
-range in air infinite
-blocked by lead/ concrete
What makes an atom radioactive
if the nucleus is unstable
-too much mass
-too much energy
- proton/neutron imbalance
What are the three experiments to test types of radiation
-penetrating power
-Range in air
-Deflection in a magnetic field
What radiation is used in smoke alarms
alpha
What radiation is used in pipe leak detection
Gamma
what radiation is used in medical tracers
Gamma (technitium 99m)
What radiation is used in monitoring material thickness
Beta