Quantum behaviour Flashcards
Photons and chance
Photons travel randomly but certain paths are more likely than others (eg straight), this leads to the more ending up in the places with higher probabilities to form brighter parts of images
Like rain, you don’t know when or where the next rain drop will fall, but if something is out in the rain it will get wet
Quanta of energy
EM radiation can be emitted and absorbed in discrete packets of energy called quanta
Planck constant equation
E = hf
= hc/λ
The electronvolt
As W=VQ
E=VQ
The energy transferred when an electron moves through a potential difference of one volt.
1eV = 1.6x10^-19 J
Photoelectric effect
When a light source strikes the surface of a metal with enough energy (independent of intensity) to overcome the work fuction
Kinetic `energy of emitted electrons
E = hf - φ
The gradient of energy versus frequency, when plotted graphically is the Planck Constant
Line Spectra
When electron changes energy levels, the absorbed or emitted photons have the same energy (E=hf) as the difference between the energy levels
Heating and cooling elements causes electrons to move between energy levels and emit photons
A diffraction grating can split the photons into their component wavelengths
The detected energies (E=hf) of these photons form line spectra and represent the different energy levels within elements
LEDs
As an electron passes through the diode it falls to a lower energy level and emits a photon
Diodes made from different semi conducting materials will release different energy photons, i.e.
Striking potential
The voltage required to make electrons drop energy levels within diodes and facilitate LEDs
Trip time
How long a photon takes to travel between two points
Photon phasor arrows
Rotate with a frequency f=E/h, all the different photons that take different paths add to form resultant phasors at different points
The angle a phasor ends up at can be worked out from the trip time and this frequency
Probability of photons arriving
Higher probability of arrival is directly proportional to the length of the resultant arrow at particular points
This leads to higher intensity at these points
Quantum reflection
Phasor arrows from paths that took a route closer to halfway along the surface will not cancel and will contribute to the magnitude of the resultant phasor
However, as less direct routes are taken the phasors from here begin to spiral, making them cancel out and contribute very little
This focuses the intensity of the reflection
Quantum refraction
Converging lens:
Light that travels straight through will go the shortest distance, however they will also have the longest path though the glass lens. In the lens the phasors rotate at a slower rate. The focal point is simply the point where all photons, from different routes, have made the same amount of rotations.
de Broglie wavelength
λ = h/p
= h/mv
