Quantum Universe - Chapter 7 Flashcards
Born Interpretation
The probability of finding a particle in an interval is given by psi squared
Copenhagen Interpretation
Observing a quantum system collapses the wave function to a specific value
What is the normalisation condition and how do you find it
Its a value that makes the wave function integrate to 1. It is found by integrating the psi value squared to 1
Why is the ground state always non zero
Due to the Heisenberg uncertainty principle
What is the expected position of a particle
<x> = Integral from minus infinity to infinity with psi squared multiplied by x
</x>
Heisenberg’s position-momentum uncertainty principle
DeltaX*DeltaP >= h-bar/2
Heisenberg’s energy-time uncertainty principle
DeltaE*DeltaT >= h-bar/2
Allowed energies (particle in box of length L)
E = E1*n^2
Potential barrier
U(x)=0 when x<0, U(x)=U0 when 0<=x<=L, U(x)=0 when x>L
What is the expectation value
The expectation value is the average value of a
quantity that requires a wave function and an
integration
What is the Heisenberg uncertainty principle explained in words
The Heisenberg uncertainty principle states that
it is impossible to simultaneously measure the
x-components of position and of momentum of
a particle with an arbitrarily high precision.
What does the energy time uncertainty principle show
The energy-time uncertainty principle
expresses the experimental observation that a
quantum state that exists only for a short time
cannot have a definite energy.
State reduction is also known as
Wave function collapse
What does Schrodinger’s equation shows according to the Copenhagen interpretation
Cat is both alive and dead, emulated superposition of particle and wave
Operator for position <x></x>
x
Operator for momentum <p>
-ih-bar d*phi/dx
Operator for kinetic energy <T></T>
-ih-bar/(2m)d^2phi/dx^2
Odd function
f(x) = -f(-x)
Non Symmetrical
Even function
f(x) = f(-x)
Symmetrical
What is the correspondence principle
Classical mechanics are an approximation of quantum mechanics for system with very large energies
Wave packet
A group of superposed waves which together form a travelling localized disturbance
What are stationary or standing waves
Their probability density function phi^2 does not vary with time
What is quantum tunnelling
Particles being able to pass through an energy barrier despite not having enough energy
What is field emission
Emission of electrons from a conducting surface due to the presence of a strong external electric field applied normal to the surface.
What is a scanning tunnelling microscope
by scanning a sharp conductive probe very close to the surface of a conductive specimen and forcing electrons to traverse the gap between them
How does a resonant tunnelling diode work
tunneling of electrons through
a finite-height potential well that occurs only
when electron energies match an energy level in
the well, occurs in quantum dots
What is a quantum dot
small region of a semiconductor
nanocrystal embedded in another semiconductor
nanocrystal, acting as a potential well for
electrons
H-bar
h/(2*pi)
ΔP or P
ΔP = sqrt(2mΔΕ)
P = sqrt(2mE)
eV to MeV/c^2
Divide by 10^6 and then multiply by c^2
MeV/c^2 to eV
Divide by c^2 and multiply by 10^6