particles of light Flashcards
what is a quantum of light
a small indivisible packet of energy = hf
What is the photoelectric effect?
The photoelectric effect is where photoelectrons are emitted from the surface of a metal after light above a certain frequency is shone on it. This certain frequency is different for different types of metals and is called the threshold frequency.
Why does the photoelectric effect occur?
- EM waves travel in discrete packets called photons, which have an energy which is directly proportional to frequency.
- Each electron can absorb a single photon, therefore a photoelectron is only emitted if the frequency is above the threshold frequency
- Each electron can absorb a single photon, therefore a photoelectron is only emitted if the frequency is above the threshold frequency
What is the work function?
The least energy needed to release a photo electron from a material = threshold energy
What is a semiconductor?
a material with conductivity between a metal and an insulator. The yare also material that have been treated so they have a low work function and respond to visible light and infrared radiation.
What is stopping potential?
The stopping potential is the potential difference you would need to apply across the metal to stop the photoelectrons with the maximum kinetic energy. Measuring stopping potential allows you to find the maximum kinetic energy of the released photoelectrons, as E V . Where is the stopping potential and is the charge of an electron. Ek (max) = e Vs where Vs is stopping potential This is derived using the fact that energy = charge * voltage .
