Photon
A quantum of light
Quantum
Packet of energy
Work function
Minimum energy needed to be gained by an electron ink order to be removed from surface of a metal
Another name for an electron when it
has been released from the surface of
a metal by the photoelectric effect.
Photoelectron
The minimum voltage needed for a
Light Emitting Diode to produce
light
Threshold p.d.
Threshold frequency
The minimum frequency of incident photons, fo
needed for the emission of electrons
from a particular metal surface
The emission of photoelectrons from a
metal surface by incident
electromagnetic radiation above the
threshold frequency.
Photoelectric effect
How to find number of photons per second
Number of Photons per sec( ph/s) = Power J/s / Ephoton ( energy of photon )J/ph
Electron volt
a unit of energy equal to the work done on an electron in accelerating it through a potential difference of one volt. 1eV = 1.602 x 10^-19 J
Number of photons per second in terms of intensity
Number of photon per second = Intensity x area / Ephoton
Two equations for photon energy
๐ธ = โ๐ ๐ธ = โc / ๐
Why under monochromatic radiation, emitted photo electrons have a range of different kinetic energies
With monochromatic radiation all photons have the same frequency and so the same energy. Each electron requires a specific energy to free it from the surface of the metal. The kinetic energy of the emitted electron is a result of the remaining energy after the electron has been freed which is dependent on how much the electrons working function is.
Do all photons with
frequencies above f0
cause electrons to be emitted?
Some electrons may transfer
energy due to interactions on their
way out, so many do not escape or
may escape with less KE.
โSome may move deeper into the
meta
What happens if you increase intensity in photoelectric effect
No effect on kinetic energy of electron but rate of photoelectron emission increases
What are the three observations from the
demonstration of the photoelectric effect and
explain how the wave model cannot account
for these observations, but the particle model
can.
- Below a certain frequency, photoelectric effect does not occur. W- assumes electrons collect energy over time. P- threshold frequency is needed
- There is no delay between light source activation and emission of photoelectrons. W- there should be a delay as electron gradually collect energy. P- it is instantaneous as electron aboarbs one photon
- Intensity of a light source has no effect on max kinetic energy. W- intensity should be proportional to kinetic energy. P- hf = E so energy only depends on frequency
How to find de Broglie minimum wavelength
Use maximum velocity
What can be explained by the wave nature of electromagnetic radiation
X-ray diffraction
