Quantum Physics NOT FINISHED Flashcards
Photon
a massless “packet” or a “quantum” of electromagnetic energy
Energy of a photon equation
E = hf
E = hc/λ
Momentum of a photon
p = E/c
The electronvolt
the energy gained by an electron travelling through a potential difference of 1V
If an electron of 1.6x10^-19C travels through 1V potential difference, then…
1eV = 1.6x10^-19
When a particle is accelerated through potential difference…
it gains kinetic energy
eV = 1/2mv^2
v = √ 2eV/m
The photoelectric effect
the phenomena in which electrons are emitted from the surface of a metal upon absorbing EM radiation
How does the photoelectric effect work
each electron can only absorb a single photon
only frequencies of light above threshold frequency will emit a photoelectron
Threshold frequency
the minimum frequency of incident electromagnetic radiation required to remove a photoelectron from the metal surface
Threshold wavelength
the longest wavelength of incident electromagnetic radiation that would remove a photoelectron from the metal surface
Photoelectric equation
E = hf = ϕ - 1/2mv^2max
hf is transferred to the electron to release it from surface and gives the photoelectron the remaining KE
Work function ϕ
the minimum energy required to release a photoelectron from the surface of a metal
Graph of photoelectric effect
- y = KE max
- x = frequency (Hz)
- work function is y-int
- no electrons emitted below the x-line
- threshold frequency is x-int
- gradient of line = h
Intensity and photoelectric current
- KE max depends on frequency of radiation, photoelectric current remains constant
- increasing no. of electrons will increase no. of photoelectrons emitted, photoelectric current increases
Photoelectric current - the no. of photoelectrons emitted per second
Photoelectric current is directly proportional to the intensity of the radiation incident
Line spectra
a phenomenon which occurs when excited atoms emit light of certain wavelengths which corresponds to different colours
