BRAINCAKEQuantum Physics
Revision notes for Quantum Physics in Edexcel Physics (8PH0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Huygens PrincipleEvery point on a wavefront is a new source of circular waves.
- Light as a WaveInterference patterns are seen when light travels through two narrow slits in Young's double slit experiment.
- Light as a ParticleIn 1887 Hertz observed the photoelectric effect.
- The Energy of a PhotonFor electromagnetic radiation the energy of a photon is the frequency multiplied by the Planck constant h.
- Electrons as WavesElectrons behave as particles as a fixed number of electrons must be removed from an atom to make an ion.
- Photoelectric EffectIf ultraviolet light is directed at a negatively charged zinc plate the plate loses its charge.
- The Equation for the Photoelectric Effecthf = φ + ½mv2max The equation is based on the conservation of energy.
- Stopping PotentialWhen light with a frequency above the threshold frequency is shone on the cathode photoelectrons will be emitted and will travel across the gap to…
- Electron DiffractionThe strongest evidence that electrons can behave as waves comes from electron diffraction.
- DeBroglie WavelengthIn 1924 Louis de Broglie suggested that if light waves can behave as particles, then particles such as electrons should also behave as waves.
- Electron MicroscopesThe smallest detail a microscope can show, its resolution, is limited by diffraction.
- Electron Energy LevelsThe electrons in an atom can only have certain definite (discrete) energies.
- Excitation and De-excitationAn electron can move up to a higher energy level if it gains exactly the right amount of energy.
- Line SpectraWhen the light from a hot, low-pressure gas (for example in a discharge tube) is passed through a diffraction grating or a prism, it does not…
- Exam Question 1Question A laser pointer emits green light of wavelength 500 nm.
- Exam Question 2Question The work function of a metal is 2.30 eV.
- Exam Question 3Question Ultraviolet light of wavelength 250 nm is shone onto the metal cathode of a photocell.
- Exam Question 4Question In an electron diffraction tube, electrons are accelerated from rest through a potential difference of 150 V and then pass through a thin…
- Exam Question 5Question Some of the energy levels of a hydrogen atom are: n = 1: −13.6 eV, n = 2: −3.40 eV, n = 3: −1.51 eV.
- Exam Question 6Question A student measures the maximum kinetic energy Ek(max) of photoelectrons emitted from a metal for light of several different frequencies f…
- Exam Question 7Question (a) Describe one piece of evidence that electrons behave as particles and one piece of evidence that they behave as waves.