Quantum Physics Flashcards
What is a Photon?
A quantum (discrete unit of energy) associated with electromagnetic radiation.
What is an Electronvolt?
The kinetic energy gained by an electron when it is accelerated through a potential difference of one volt.
What is meant by the term Threshold Frequency?
The lowest frequency of radiation that will result in photoelectron emission from a particular metal surface.
What apparatus is used to show the photoelectric effect?
- A gold leaf electroscope with a brass stem, a gold leaf and a metal cap
- A metal (usually zinc) plate placed on top
What happens when a negatively charged polythene rod touches the metal plate of an electroscope?
The metal stem and gold leaf become also become negatively charged causing them to repel each other.
What happens when radiation above the threshold frequency of the metal comes in contact with the metal plate?
The leaf falls since it loses electrons and therefore has a negative charge.
What is the Work Function of a metal?
The minimum energy required to release an electron from its surface, overcoming the attraction between the electron and positive metal ions.
What happens to excess energy an electron gains above the work function?
It becomes kinetic energy
Does the Intensity of radiation affect Photon Energy?
No, only the frequency of radiation affects photon energy, intensity only affects the amount of photons.
What is Wave-Particle Duality?
The theory that all objects can exhibit both wave and particle properties.
How can electrons behave like waves?
When electrons are fired from an electron gun at a florescent screen, going through polycrystalline graphite, causing a circular diffraction pattern, a property usually only shown by waves.
