Quantum Flashcards
What is specific charge?
The ratio of charge to mass
Describe the strong nuclear force
It is short ranged
It is attractive up until 3 fm after which it rapidly falls to zero
Below 0.5 fm it is repulsive
What are electronvolts?
Unit to measure energy of photons
Energy in eV = energy in joules/
1.6×10^-19
Describe beta-minus decay
A neutron in the nucleus changes into a proton. A fast moving electron is emitted from the nucleus along with an antineutrino.
What is ionisation?
When an electron gains enough energy to be removed from the atom.
How do fluorescent lamps work?
They contain Mercury vapour
A high voltage is applied across the lamp which accelerates free electrons passing through the lamp. These then collide with the electrons in the Mercury vapour atoms, causing them to excite.
Each excited electrons then de-excited, emitting a photon of energy equal to the energy difference between the energy levels. These photons are in the UV region.
The lamp has a phosphorus coating which absorbs the UV photons, exciting the coatings electrons. These atomic electrons de-excite indirectly to lower energy levels, emitting lower energy photons.
Describe emission line spectra
Each spectral line corresponds to an electron falling down to a lower energy state. They occur when the light from a fluorescent lamp is directed at a diffraction grating.
Describe absorption line specrta
Occurs when light with a continuous spectrum passes through a cold gas. Photons of specific frequencies are absorbed by electrons in the atoms of the cold gas, exciting them to higher energy levels. These frequencies are then missing from the spectrum.
What is line spectra evidence for
That electrons in atoms are in discrete energy levels.
What is the evidence for light being both a wave and particle?
Diffraction is evidence for it being a wave
The photoelectric effect is evidence for it being a particle
What is the evidence for electrons being both a wave and particle?
Diffraction pattern is evidence of it being a wave
Being deflected in an electric field is evidence of it being a particle
What is the threshold frequency?
The minimum frequency of radiation needed to liberate an electron from the surface of a metal.
