Nature of Light Flashcards
What is a photon?
A package (quantum) of electromagnetic energy.
What is the work function?
The minimum energy required to release the photoelectron from the metal surface. For photoelectric emission to occur, the energy of the photon must be equal to or greater than the work function
What is the threshold frequency?
If the photon’s energy is just enough to release a photoelectron
What the ground state?
When an electron moves from a state where the atom has the most energy to one where it has the least, known as the ground state
What is radiation flux?
The rate at which a beam of light supplies energy to a particular area. It’s also known as intensity.
How do you measure efficiency?
Useful energy output/total energy input
Considerations for energy sources
Efficiency of the cells Cost Availability of materials Global energy prices Impact of continuing use of fossil fuels
What is the main problem with solar cells?
Useful in countries with guaranteed sunshine most of the year. Until more efficient ones are developed, they cant be used in countries with poor weather and it can be very expensive to pay for the development of efficient cells.
What is photo electric emission
When a single photon is absorbed by a metal surface, its energy is transferred to a single electron, which may then be released from the metal. The released electron is the photoelectron
What is the wave model
Wave model predicts that weak radiation would eventually release large numbers of electrons with low energy, but this is not what happens.
Describe photon model.
Weak radiationo causes instantaneous release of some electrons if the frequency is greater than the threshold frequency. The ke of individual photo electrons depends only on the freq of the radiations, not its intensity
Describe stopping voltage
If the metal surface is connected to a positive potential, the photo electron is attracted back to it. To escape from the surface, the ke of the photo electron is used to do work against the electrostatic force. If the potential is increased, eventually even the most energetic electrons fail to escape and the potential is called the stopping voltage
