Quantum Flashcards
What is thermionic emission?
Electrons break off a material due to heating
What is an electron volt?
1.6x10^-19 joules
What is the threshold frequency?
The minimum frequency of electromagnetic radiation to cause electrons to break off a metal F0
What is photon energy?
E =hf
h is Planck’s constant
What is Planck’s constant?
6.63x10^-34
What is the work function? φ
φ is the minimum amount of energy needed for an electron to break off the metal
What is the other equation for photon energy?
hf = φ + 1/2 *mv^2
What is a quanta?
A discrete packet of EM radiation
How ( in what state ) do electrons exist?
In discrete energy levels given by numbers
How can an electron move down energy levels?
By emitting a photon
When changing energy levels, what is the photon energy = to?
The difference between energy levels of the electrons
How do electrons move up a level? (excited)
By absorbing a photon with an exact energy difference
What is the spectrum of light
Continuous
What happens when you heat up a gas?
Electrons become excited and move up an energy level
How do you get a line emission spectra?
Send white light through a hot gas with a prism you will get a line emission spectra
What is a line emission spectra?
Series of bright lines on a blank background.
What does each line represent on a line spectra?
The frequency that corresponds to the electron’s energy levels
How do you get a line absorption spectra?
White light passes through through a cool gas and then a prism or diffraction grating
What happens when electrons are at a low temperature?
The majority return to the ground level
What is the relationship between emission and absorption spectra?
The black/coloured lines represent the same thing and would be in the same places
What are photons?
Packets of energy being delivered (similar to particles)
What is brightness?
A greater quantity of photons, not a greater amount of energy
What is the relationship between photon energy and wavelength
E =hf f =c/λ
E =h* c/λ
So λ is indirectly proportional to E
What is the stopping voltage?
Vs = (hf- φ)/q
What is De Broglie’s wave-particle duality theory?
If light exhibits both wave and particle-like properties, then electrons should too its the wavelength given to particles
What is De Broglie’s λ equation?
DB λ = h/ ρ ρ=momentum and h = P constant
What is De Broglie’s λ?
The probability of finding a particle at a point and the wavelength given to particles
How were electron diffraction patterns discovered?
Voltage used to accelerate the electrons through graphite
What is the structure of graphite?
Formed in layers with very small gaps
What happens is you decrease the accelerating voltage?
Decreases DB λ so λ is similar to gap length so more diffraction
What is a condition for diffraction?
If DB λ has to be similar to the gap length
Why do energy levels have negative values?
As energy must be supplied to the system for the electrons to overcome the nucleus’ attractive force
What are spectral lines caused by?
Electrons moving to a higher energy level and then back to a lower energy level emitting a photon
