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what is Photoelectric effect?
Where one free electron on a metal's surface absorbs energy from one photon
What is the emitted electron called?
Photoelectron
What happens if the frequency is enough (>threshold frequency) + the energy is enough (>work function)?
The electron is released
what is 1eV equivalent to in joules?
1.6x10^-19 J
Unit for electron energy ?
Electron volt (eV)
What is 1eV (definition) ?
The energy transferred when an electron travels through a potential difference of 1 volt.
h x f =
Φ + Ek (max)
What is Work function ?
Minimum energy to remove electron from the metal's surface
What is Threshold frequency?
Minimum frequency needed to remove an electron from the metals surface
At the minimum threshold to free an electron: kinetic energy = what ?
0
The gradient of a KE:f graph = what ?
Planck's constant
How can a circuit be used to find the maximum kinetic energy for photoelectrons?
A potential difference is increased in the opposite direction to the way the electrons are moving.
When the electrons just fail to reach the anode, the stopping potential has been reached.
Ek(max) = eV(stop)
What is the excess energy in photoelectric effect called ?
kinetic energy
What is Excitation?
Electrons moving up energy levels
What is De-excitation ?
Electrons moving down energy levels
What does Change in Energy = ?
Planck's constant x frequency
What is Ionisation ?
The electron escapes completely from the top energy level of the atom
What is Ionisation energy ?
The minimum energy needed to completely free an electron from an atom
How else can we ionise gas atoms?
By applying a voltage
How do fluorescent lights work?
They generate UV radiation which is absorbed (mercury vapour) and re emitted as visible light by a layer of phosphorus inside the bulb
(De Broglie) wavelength = ?
Planck's constant / momentum
Electrons interfere in a ____ _________ pattern.
Wave interface
Greater momentum (from faster electrons) means ?
Smaller de Broglie wavelength
Note
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