13. Quantum physics (4.5) Flashcards
(21 cards)
What is a photon?
A discrete quantum packet of energy in the form of electromagnetic radiation
Equation for energy of photon
E=hf
E=hc/λ
Where h = Planck’s constant and f = frequency
What is the numerical value of Planck’s constant
6.63 x 10^-34
What are the units of Planck’s constant?
Js
Is eV a unit of charge?
No it’s a unit of energy.
How many joules is 1 eV?
1.6 x 10^-19 J
PAG 6
Photoelectric effect
When EM radiation is shone at a metal, and then the metal emits photoelectrons since electrons gain the energy of the EM radiation and become liberated from their energy levels.
Remember the gold leaf thing and photoelectric effect
How many photons interact with each electron
One photon interacts with one electron (1 to 1)
What is Einstein’ photoelectric equation?
hf = Φ + KE (max)
Where Φ = the work function (in joules)
What is the work function of a material?
The minimum energy required for an electron to be liberatied
Definition of threshold frequency.
The frequency of the photon at which it’s energy is equal to the work function
Formula of threshold frequency:
f(zero) = Φ/h
Does the max kinetic energy of the photoelectric depend on intensity of incident radiation?
No, it only depends onthe frequency of radiation (and work function of the material)
What does an increase in light intensity lead to in photoelectric emissions?
An increase in the rate of emission
They are directly proportional
What does electron diffraction show about electrons?
Provides evidence of wave-like behaviour of particles
Why is is significant that electrons are diffracted by a slice of graphite?
It means that the wavelength if electrons is of the same magnitude (similar size) as the distance between atoms (roughly 10^-10)
What is the de Broglie equation?
λ = h/p
Where p = momentum
Wavelength of an electron in terms of mass, Planck’s constant, and KE:
λ = h/√(2m*KE)
