A2 Physics Quantum Physics

what is a photon

a quantum of energy when the energy is in the form of electromagnetic radiation

formula for photon energy

convert from electron volt (eV) to joules (J)

multiply by 1.6 × 10^-19

formula for momentum of photon

what are emitted from a metal surface when illuminated by electromagnetic radiation

photoelectrons

what is threshold frequency

minimum frequency of incident electromagnetic radiation required to remove a photoelectron

what is threshold wavelength

longest wavelength needed to remove a photoelectron

formula for photoelectric emission

what is the effect of intensity on maximum kinetic energy of photoelectrons

there is no effect because increase in intensity only increases the number of photoelectrons leaving the surface

what is the effect of intensity on photoelectric current

they are proportional because photoelectric current refers to number of photoelectrons emitted which increases with intensity

what is photoelectric effect

emission of electrons when electromagnetic radiation is incident

what is work function energy

minimum energy for an electron to leave the surface

explain the evidence provided by the electron diffraction for the wave nature of particles

what is de Broglie wavelength

the wavelength associated with a moving particle

formula for de Broglie wavelength

how do you describe the electron energy levels in isolated atoms

they are discrete

how does emission and absorption line spectra look like

how is an emission spectra made

• electron transitions from higher energy level to lower energy level → emission of photon

• represented by coloured lines in a black background

how does an absorption spectra form

• when an electron transitions from low to high energy → due to absorption of photon

• a continuous spectrum with black lines at certain wavelengths

formula for difference between two energy levels