Quantum Physics Flashcards
(34 cards)
What is the photoelectric effect?
The emission of electrons from a metal when photons of light with sufficient energy (greater than the work function) are incident on the surface.
What is a photon?
A packet of light energy.
Define threshold frequency fo.
The minimum frequency that will cause photoelectric emission in a particular metal (Hz).
Define work function.
The minimum energy needed to remove electrons from a metal. (J)
How is work function calculated?
Ф = h fo
State Einstein’s photoelectric equation.
photon energy = work function + KE of electron.
E = Ф + KE
E = Ф + ½ m v² (all J)
State Planck’s equation.
E = h f
where E = energy of a photon (J), h = Planck’s constant (Js), f = frequency (Hz)
How do you change from J to eV?
energy in eV = energy in J / 1.6 × 10^-19
State the version of Einstein’s Photoelectric equation where stopping voltage is mentioned.
E = Ф + q Vs
where q = the charge on an electron (C) and Vs = the stopping voltage (V)
What will a graph of Vs against f look like?
What will a graph of KEmax against f look like?
How is an absorption spectrum formed?
Some wavelengths of light are absorbed as they pass through a hot gas. Electrons are jumping up the energy levels.
(Coloured background black lines)
How is an emission spectrum formed?
Some wavelengths of light are emitted from a hot gas. Electrons are falling down the energy levels.
(Black background, coloured lines)
State the formula giving the energy released/absorbed when electrons move between energy levels.
h f = E2 - E1
where E2 - E1 is the difference between the energy levels.
Define ionisation energy.
The amount of energy required to release an electron from its ground state, right out of the atom.
What does Laser stand for?
Light Amplification by the Stimulated Emission of Radiation.
What are the 2 main ways X-rays are produced?
- Braking Radiation
- Line Emission Spectrum
What does a typical X-ray spectrum look like?
What is the formula for the max energy of an X-ray?
Max E = hc / Amin
What does CT stand for?
Computed Tomography
Which phenomenon are indicative of wave behaviour?
Interference, diffraction and polarisation.
Which phenomenon is indicative of particle behaviour?
Photoelectric Effect
