P3 - Photoelectricity Flashcards
Why can’t threshold frequency be explained by wave theory?
Suggests that the frequency of light should be able to cause photoelectric emission
How does the light model explain photoelectric emission?
EM waves travel in photons
- Each electron can absorb a single photon, therefore a photoelectron is only emitted if its frequency is above the threshold frequency.
What effect does increasing light intensity have on photoelectron emission?
More photoelectrons are emitted per second.
Define stopping potential
The potential difference needed to stop photoelectrons with the maximum kinetic energy.
What is ionisation?
When electrons gain enough energy to be removed from the entire atom completely.
Describe the fluorescent tube practical.
- Free electrons collide with mercury atoms, ionising them, and releasing more free electrons
- Free electrons excite mercury atoms
- When they de-excite photons are released: UV Range
- Fluorescent coating absorbs UV photons, exciting electrons and then deexciting releasing photons of visible light
Define an Electron Volt
Energy is gained by one electron when passing through a potential difference of one volt.
