Quantum Theory Flashcards
What are the three theories that cannot be explained by classical physics but can be explained by quantum theory?
Black body radiation
Photoelectric effect
Emission/absorption spectra
What is the photoelectric effect?
When EM radiation incident on a metal causes electrons to be emitted (photoemission)
What could classical theory not explain in the photoelectric effect?
A bright, low frequency light did not produce photoemission
There was no time delay for a dim UV light to produce photoemission
What are evidence for electrons and EM radiation showing wave-particle duality?
Photoelectric effect
Compton scattering
Interference of EM radiation
What is evidence for particles displaying wave behaviour?
Electron diffraction
-electrons can be shown to diffract through Crystal lattice if the De Broglie wavelength is similar to grating/lattice spacing
When does diffraction occur (De Broglie wavelength)
When a particle passes through a gap that has a similar size to its De Broglie wavelength
What does the uncertainty principle state?
It is impossible to determine accurately the position and momentum of a quantum particle simultaneously.
What is quantum tunnelling?
There is a finite possibility that an object trapper behind a barrier without enough energy to overcome the barrier may appear on the other side of it
What is the force on a charged particle moving perpendicular to a magnetic field perpendicular to?
Both the B-field and direction of travel
Why do particles follow a helical path?
The perpendicular component of velocity results in circular motion
Parallel component of velocity is constant causing it to move forward
What are cosmic rays?
High energy subatomic particles which arrive in earths atmosphere from outer space
What are cosmic rays composed of?
89% protons
9% alpha particles
1% carbon, oxygen and nitrogen nuclei
Remainder electrons and gamma rays
What happens when cosmic rays hit the top of the atmosphere?
They produce cosmic air showers of particles
What is a solar wind?
A stream of charged particles which escape from the upper atmosphere of the sun
It moved at a high speed and consists mainly of electrons, protons and alpha particles in the state of plasma
What is simple harmonic motion?
An oscillation where an object repeats a motion about an equilibrium position under the influence of an unbalanced force which is
- always directed towards equilibrium position
- proportional to displacement from equilibrium position
