What is quantum question mark. state the energyof one Quantum of radiation?
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Physics > Dual Nature of Radiation and Matter > Einstein’s Photoelectric Equation: Energy Quantum of Radiation
Dual Nature of Radiation and Matter
Einstein’s Photoelectric Equation: Energy Quantum of Radiation
In 1905, the annus mirabilis (miracle year) of Physics, Albert Einstein proposed an equation to explain this effect. Einstein argued that light was a wave that interacts with matter in the form of a packet of energy or a quantum of energy. This quantum of radiation was a photon and the equation was called Einstein’s photoelectric equation.
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According to Einstein's interpretation of the photoelectric effect, the maximum K.E. of photoelectrons depends on ( h -W) where is the frequency of incident radiation and W is the work function. For three different metals graph plotted between maximum K/E. and the frequency of incident radiations. The three graphs obtained:
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A photon will have less energy, if its :
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Einstein's photoelectric equation state that hv=W_0 + E_khv=W
0
+E
k
In the equation, E_kE
k
refers to the
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Einstein’s Photoelectric Equation
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Einstein’s Photoelectric Equation.
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The Photoelectric Effect
Let us recall the Photoelectric effect.
Firstly, above a specific value of the frequency (threshold frequency), the strength of the photoelectric current depends on the intensity of the light radiation.
The reverse potential at which the photo-current stops (stopping potential) is independent of the intensity of light. Therefore, no matter how intense your source of light is, it can’t defeat the stopping voltage.
Any values of frequency below the threshold value are unable to produce a photoelectric current. Therefore, even if you take a metallic strip to the surface of your nearest star (Sun), you will never get a photocurrent if the frequency of the radiation is smaller than the threshold frequency.
The photoelectric effect was almost instantaneous. This meant that as soon as you turn your source of light on, pop goes the electron!
Quantum of Radiation
Enter Einstein and His Equation of The Photoelectric Effect
Einstein’s view of light was magnificent as well as revolutionary. He proposed a weird but effective model of radiation. Light consisted of very small particles. These particles were not matter but pure energy. He called each of these a quantum of radiation. Therefore, light must be made up of these quantas or packets of energy or quantum energy. We call them photons and they carry the momentum and energy from our source of light.
According to the Einstein-Plank relation, we have E = hν …(1)
Where ‘h’ is the Plank’s constant and ‘ν’ is the frequency of the radiation emitted.
Also from the experiment on Photoelectric effect, we see that there is a threshold frequency below which the electrons won’t come out of the metallic surface. In equation (1) we see that Energy is a function of frequency. Hence this observation is explained by equation (1). This also explains the instantaneous nature of the photoelectric emission.
Quantum is not an energy or radiation it is called as Quantum number which is used in the atoms.