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The photoelectric effect has three important characteristics that cannot be explained by classical physics: (1) the absence of a lag time, (2) the independence of the kinetic energy of photoelectrons on the intensity of incident radiation, and (3) the presence of a cut-off frequency. Let’s examine each of these characteristics.
Figure 29.3.1 29.3. 1: The EM spectrum, showing major categories as a function of photon energy in eV, as well as wavelength and frequency. Certain characteristics of EM radiation are directly attributable to photon energy alone. Photons act as individual quanta and interact with individual electrons, atoms, molecules, and so on.
The above formula is applicable to a single photon. When more photons are emitted, consider n number of photons, then the formula is given by: E = n × h × f. Energy is calculated in Joules and electronvolt (eV), depending on the system of the unit used. 1 Joule = 6.24 × 10 18 eV.
- The amount of energy is directly proportional to the photon’s electromagnetic frequency.
- 1 Joule = 6.24 × 10 18 eV
- The photoelectric effect was discovered by the scientist Albert Einstein.
- The formula to find the maximum kinetic energy of ejected electrons is: \(\begin{array}{l}KE_{e} = hf – BE\end{array} \)
Photon energy. Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. Equivalently, the longer the photon's wavelength, the lower ...
For now, we will use the photon concept to explain the photoelectric effect, much as Einstein did. Figure 29.2.2 29.2. 2: An EM wave of frequency f f is composed of photons, or individual quanta of EM radiation. The energy of each photon is E = hf E = h f, where h h is Planck’s constant and f f is the frequency of the EM radiation.
A photon is a quantum of EM radiation. Its energy is given by E = hf and is related to the frequency f and wavelength λ of the radiation by. E = hf = hc λ (energy of a photon) E = h f = h c λ (energy of a photon), where E is the energy of a single photon and c is the speed of light. When working with small systems, energy in eV is often useful.
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The kinetic energy KE of an ejected electron equals the photon energy minus the binding energy BE of the electron in the specific material. An individual photon can give all of its energy to an electron. The photon’s energy is partly used to break the electron away from the material. The remainder goes into the ejected electron’s kinetic ...
