EM radiation and Quantum Phenomena Flashcards
What is a photon?
A discrete packet of energy
E = hf
Define the term threshold frequency
The minimum frequency of light which causes electrons to be emitted from the surface of a metal
Define the term work function
The minimum energy needed to remove an electron from the surface of a metal
Define the term stopping potential
The minimum potential applied to a metal surface to reduce the photoelectric current to zero when monochromatic light is incident on the surface
What is the photoelectric effect?
The emission of electrons from a metal surface when the surface is illuminated by a light of frequency greater than the threshold frequency
Define excitation
A process where electrons move to a higher energy level
Define de-excitation
Where electrons move to a lower energy level
Define ionisation
A process where an electron gains enough energy to leave the atom
How do fluorescent tubes work
A PD is put across mercury atoms. Ionisation occurs and electrons are emitted. UV photons are emitted. UV is absorbed by fluorescent coating which gets excited and emits visible photons
Why are energy levels negative
Since work has to be done to move them to the ionisation level and become free
What is wave particle duality
A particle has properties of a wave and vice versa
What proves that a particle is a wave?
Electron diffraction, an electron passes through a slit, the electron turns into a wave and diffracts
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