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Photons and Electrons
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Detailed summary of all key points involving photons and electrons. Easy and simple to understand.
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Photons and electronsLight travels as a wave but transfers energy as a particle.
Quantum theory: light has wave and particle nature.
Frequency: amount of energy each photon has. Total number of waves which pass a
specific point per second. IR(ROYGBIV)UV
Speed of a wave (v): distance covered by the wave per unit time (per second.)
Intensity: number of photons per second/brightness.
Work function (Wo) – relates to the metal: minimum amount of energy needed to
emit an electron from the surface of a metal.
Threshold frequency (fo) – relates to photon: minimum frequency of incident
radiation at which electrons will be emitted from a particular metal.
Wavelength: distance between 2 crests or 2 troughs (maximum or minimum points.)
Electromagnetic Radiation
Light is an EM.
A particle of light is a packet of energy called a photon.
Energy of a photon of light is directly proportional to the frequency of the light.
Wavelength and frequency are inversely proportional.
As frequency increases, wavelength decreases.
Light travels at a constant speed in a vacuum c = 3 x 108 m. s−1
c
f=
λ
f = frequency (Hz)
λ = wavelength of light (m)
Energy of a photon (J)
hc
E = hf or E =
λ
h = plancks constant of 6,6 x 10−34 J . s
Energy of photon is directly proportional to frequency.
Energy of a photon is inversely proportional to wavelength.
As energy increases, wavelength decreases and visa versa.
ROYGBIV – energy increases
Electron volt (eV)
Unit of energy.
To convert electron volts to joules, multiply by 1,6 x 10−19
To convert joules to electron volts, divide by 1,6 x 10−19
The photoelectric effect
Process that occurs when light shines on a metal and electrons are ejected.
For electrons to be emitted, the light must have sufficient energy.
Work function (Wo) – relates to the metal: minimum amount of energy needed to
emit an electron from the surface of a metal.
Threshold frequency (fo) – relates to photon: minimum frequency of incident
radiation at which electrons will be emitted from a particular metal.
Threshold frequency corresponds to maximum wavelength ( λ o) which will cause an
electron to be emitted.
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