Photoelectric Effect Flashcards
What is photoelectric effect?
Emission of electrons from a metal when light of a high enough frequency is shone on it.
Threshold frequency
The minimum frequency required to cause photoemission
Stopping potential
Potential difference needed to stop the fastest moving electrons travelling with kinetic energy.
Fluorescent tubes
Electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow.
High voltage in FT
Accelerates fast-moving free electrons that ionise mercury atoms, producing more free electrons. Free electrons collide with mercury electrons which are excited to a higher level.
Phosphor coating?
Absorbs photons exciting electrons to much higher levels. Electrons then go down energy levels and lose energy by emitting lower energy photons of visible light
Diffraction
Beam of light passes through a narrow gap, it spreads out.
Work function unit
Joules
Work function definition
Minimum energy required to remove an electron from the surface of the material
WF equation
H x threshold frequency
Calculate max kinetic energy
h x f - W
Explain why only photons of certain frequencies cause excitation in a particular atom.
Only one photon can be absorbed by one electron to make the jump in between levels.
Process which mercury atoms excited in FT
pass through the fluorescent tube, they collide with the mercury atoms within it and this collision transfers energy to the atom. This energy transfer allows the atom’s orbiting electrons to move to a higher energy state thus exciting the atom.
