Colin Donnelly-
What did Einstein win the Nobel Prize for?
photoelectric effect
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Photoelectric effect
The emission of electrons when electromagnetic radiation, such as light, hits a material
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Electrons liberated from a metal by the photoelectric effect will produce a _____, or _____.
net charge flow per unit time, or current
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Provided that a light beam’s frequency is above the threshold frequency of a metal, light beams of greater _____ produce _____ via the photoelectric effect.
intensity
larger current
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When light’s frequency is above the _____, the magnitude of the resulting current is _____ of the light beam.
threshold frequency
directly proportional to the intensity (and amplitude)
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Threshold frequency
The minimum frequency of light that causes ejection of electrons is known as the threshold frequency, fT.
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The threshold frequency depends on the _____ being exposed to the radiation.
type of metal
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If the frequency of the incident photon is less than the threshold frequency (f < fT), then _____ will be ejected because the photons ...
no electron
... do not have sufficient energy to dislodge the electron from its atom.
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If the frequency of the incident photon is greater than the threshold frequency (f > fT), then an electron will be ejected, and the maximum kinetic energy of the ejected electron will be equal to ...
... the difference between hf and hfT.
(also called the work function)
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Planck Relation
E = hf
E is the energy of the photon of light
h is Planck’s constant (6.626 × 10−34 J·s)
f is the frequency of the light
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Einstein’s explanation of the results of the photoelectric effect was that the light beam consists of _____.
an integral number of light quanta called photons
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Photon
An elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.
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Waves with higher frequency have _____ and _____.
shorter wavelengths and higher energy
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Angstrom
1 Å = 10−10 m
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In nuclear physics, wavelength is commonly measured in _____ and _____.
nanometers
ångströms
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The reason that we only discuss electrons being ejected from metals (and not protons or neutrons) is because of ...
... the weak hold that metals have on their valence electrons due to their low ionization energies.
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If the frequency of an incident photon is above the threshold frequency of the metal, the photon will have more than enough energy to eject a single electron, and the excess energy will be converted to _____.
kinetic energy in the ejected electron
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If the frequency of a photon of light incident on a metal is at the threshold frequency for the metal, the electron _____.
barely escapes from the metal
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Kinetic energy of an ejected electron equation
Kmax = hf − W
W is the work function of the metal in question
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Work function
W = hfT
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Kmax is only achieved when ...
... all possible energy from the photon is transferred to the ejected electron.
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The actual energy of an ejected electron can be _____.
anywhere between 0 and Kmax
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The speed of ejected electrons is affected by its _____, not its _____.
frequency (color)
intensity
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Classical physics _____ explain the photoelectric effect because ...
cannot
... the effect only works if light acts as a discrete bundle of energy, not a continuous flow.
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When the frequency of incident light on a metal is increased, _____ increases because ...
Kmax
The excess energy of photons is translated to kinetic energy of the ejected electrons
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When the intensity of incident light increases, _____ increases but _____ does not increase. this is because ...
current increases, but not Kmax
... there are more electrons being ejected from the metal due to more incident photons, but because the energy of the photons is not increasing there is not as much excess energy to translate to kinetic energy.
