Physics - Recall for Chapter 13; Quantum Physics
Recall Questions
What is a photon?
A quantum of energy of electromagnetic radiation.
What is the photoelectric effect?
The emission of electrons from a metal surface when illuminated with light.
What is a photoelectron?
An electron that has been removed from a metal by absorbing a photon.
What is the work function?
The minimum energy required to release an electron from the surface of a metal.
What is the threshold frequency?
The minimum frequency of light required to produce photoelectrons from a metal.
What is monochromatic light?
Light of a single frequency/wavelength.
What is required for a photon to be able to produce photoelectrons?
Its frequency is greater than the threshold frequency.
Why can’t light sources below the threshold frequency produce photoelectrons?
The photon eneergy is less than the work function.
How do photons and electrons interact?
A signle photon can be absorbed/emitted by a single electron which gains/loses the energy of the photon.
What is the effect on an electron of absorbing a photon?
The electron gains the energy of the photon.
What effect does increasing the frequency of a monochromatic light source have on photoelectrons produced?
Photoelectrons will have a greated maximum kinetic energy.
What is the effect of increasing the intensity of a monochromatic light source on photoelectrons produced?
More photoelectrons will be produced but they will have the same maximum kinetic energy.
What two factors determine the maximum kinetic energy of photoelectrons?
The frequency of the light and the work function of the metal.
What is $KE _ \text{max}$ in Einstein’s photoelectric effect equation ($hf = \phi + KE _ \text{max}$)?
The maximum kinetic energy of the photoelectrons.
According to the wave model, how is energy transferred from light to electrons in a metal?
It is delivered continuously and builds up over time.
If light is above the threshold frequency, how long will it take for photoelectrons to start being produced?
It is instantaneous.
What happens if very intense light that is below the threshold frequency is used?
No photoelectrons are produced, regardless of intensity.
What determines the energy of a photon?
The frequency/wavelength.
How do you calculate the energy of a photon?
or
\[E = \frac{hc}{\lambda}\]What is an electron volt?
The energy gained or lost by an electron passing through a potential difference of $1V$.
What is the threshold p.d. of an LED?
The minimum potential difference required for the LED to produce light.
How can the threshold p.d. of an LED be used to find photon energy?
The energy transferred by the electrons ($eV$) is equal to the energy of the photons produced ($hf$).
What is meant by wave-particle duality?
It describes how all matter can display both wave and particle properties.
What is the key piece of evidence for wave-particle duality?
When an electron beam passes through polycrystaline graphite, it produces a diffraction and interference pattern.
What is the relationship between momentum and wavelength?
Inverse proportionality.