12 Quantum Physics Flashcards
12 Quantum Physics
energy of photon
E = hf = h(c/λ)
evidence for light as wave
light exhibits wave phenomena such as diffraction and interference
what is the photoelectric effect
When light above a certain frequency is shone on a metal plate electrons are emitted.
the KE of emitted photoelectrons depends on
the frequency of the EM radiation
What is the threshold frequency (f0)?
the minimum frequency of light needed for giving electrons enough energy to escape the metal surface
electrons are only ejected when the frequency of the light is above f0, why does this support the particle theory of light?
one electron interacts with one photon particle, so each photon needs to have enough energy
explain why stopping voltage is a direct way of measuring KEmax (eVs = KEmax)
E = qV = eV
define de Broglie wavelength
λ = h/p = h/mv = h/√2MeV
De Broglie wavelength is the wavelength associated with a moving particle
show that angular momentum is quantized
for an electron to exist in an atom only whole de Broglie wavelengths are allowed:
2πr = nλ = n(h/mv)
mvr = n(h/2π)
what can the Schrodinger wave function (Ψ) tell us?
The square of the wavefunction (Ψ²) gives the probability of finding the particle in a region
define photon
quantized packets of energy
equation for the photoelectric effect
Ephoton = Eelectron = hf = KEmax + φ
explain the photoelectric effect
Light consists of photons with energy E = hf. If the energy of the photon is large enough, it gives the electron enough energy to escape from the surface (φ). Any extra energy is retained be the electron as KE.
the number of emitted photoelectrons depends on
the intensity of the EM radiation
E = hf = KEmax + φ
Why does it say maximum KE?
if electrons are buried deeper inside the metal → larger work function φ → smaller KE
