![]() Another common form of this equation is in terms of wavelength using c = νλ, E = \frac = 5.50 × 10 -19 J/e – + E KE of ejected electronsĮ KE of ejected electron = 1.12 × 10 -19 J/e – Blackbody Radiation and the Ultraviolet Catastrophe For any frequency of light above the threshold frequency, the kinetic energy of ejected electron will be proportional to the energy of the incoming photon.Įinstein argued that the light striking the metal surface should not be viewed as a wave (as in the view of classical wave theory), but instead as a stream of particles (later called photons) whose energy depends on their frequency according to the equation, E = hν (where h is a fundamental physical constant known as Planck’s constant, 6.626 × 10 -34 J Photons with low frequencies do not have enough energy to cause electrons to be ejected via the photoelectric effect. In 1905, Albert Einstein was able to resolve the paradox. Scientists did note, however, that the intensity of the light did affect something-the number of electrons ejected in a given time period. ![]() Therefore, a pure classical wave theory explanation of the photoelectric effect was not possible. Therefore, if the photoelectric effect were to be explained in terms of classical wave theory, changing the intensity of the incident light should have determined whether electrons could be ejected, not the frequency. Thus, the incident light needed to have more energy than the binding energy in order to free the electrons.Īccording to classical wave theory, a wave’s energy depends on its intensity (which depends on its amplitude), not its frequency. T he electrons in the metal had a certain amount of binding energy keeping them bound. They observed that electrons could only be ejected when the frequency of the incident light was greater than some threshold frequency, and that the kinetic energy of the ejected electrons increased with increasing frequency of the incident light. This phenomena is called the photoelectric effect ( Figure 1). It had been observed since the late 1800s that electrons could be ejected from the clean surface of a metal if irradiated with light. | Key Concepts and Summary | Key Equations | Glossary | End of Section Exercises | The Photoelectric Effect | Photoelectric Effect | Blackbody Radiation and the Ultraviolet Catastrophe | Evaluate the evidence for the particle nature of light as revealed by the photoelectric effect. ![]()
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