Quantum Flashcards
What is a photon?
A discrete packet or quantum of electromagnetic energy
What is an electron volt?
The energy gained by an electron when accelerated through a potential difference of 1 volt
How do you convert joules to eV?
Divide by 1.6x10^-19
How do you convert eV to joules?
Multiply by 1.6x10^-19
Name 3 quantised values
Electron energy levels, electric charge, photon energy
What is ground state?
The lowest possible energy level an electron can occupy
What is excitation?
When an electron moves up energy levels by absorbing a specific amount of energy from an electron or photon
What is de-excitation?
When an electron moves back down energy levels by emitting a photon with a specific amount of energy
What is ionisation?
When an electron gains enough energy to completely escape an atom
What is a continuous spectrum?
A spectrum where all frequencies are present
What is a line spectrum?
A spectrum of discrete coloured lines of light
What is an emission spectrum?
A bright spectrum seen when photons are emitted from atoms, corresponding to the frequencies emitted by a gas
What is an absorption spectrum?
A spectrum of dark lines on a coloured background corresponding to the frequencies absorbed by a gas
What is fluorescence?
When a substance absorbs high energy photons and emits low energy photons
What is plasma?
A mixture of ions and electrons in a gas
What is thermionic emission?
When a heated cathode releases free electrons from its surface
What first provided evidence for light having particle properties?
The photoelectric effect
What is threshold frequency?
The minimum frequency of light to release an electron from the surface of a metal
How many photons can one electron absorb?
1
What is the work function?
The least amount of energy required to release a photoelectron from the surface of a material
Why does the kinetic energy of photoelectrons vary?
Electrons deeper in a material use energy to move to the surface first, so have less left over kinetic energy
What is the stopping potential?
The potential difference at which removed electrons do not reach the opposite plate
That is observed in the photoelectric effect if frequency is decreased?
Electrons have less energy so less are removed from the surface of the metal, and current decreases
What is observed in the photoelectric effect if intensity is decreased?
There are less photons so less electrons are given energy and less are removed, so current decreases
What is saturation current?
The maximum current as there are no more electrons available to be released
What provides evidence for the wave-particle duality of electromagnetic radiation?
Diffraction (wave property) and photoelectric effect (particle property)
What provides evidence for wave-particle duality of electrons?
Electron diffraction (wave property)
What is the de Broglie wavelength?
The wavelength associated with moving particles
