Acdc radiant energy examples9/5/2023 ![]() ![]() As things turned out, Planck’s hypothesis was the seed from which modern physics grew.įigure 2.2.3 The Photoelectric Effect (a) Irradiating a metal surface with photons of sufficiently high energy causes electrons to be ejected from the metal. In time, a theory might be developed to explain that law. If quantization were observed for a large number of different phenomena, then quantization would become a law. Initially, his hypothesis explained only one set of experimental data-blackbody radiation. (you may need to install JAVA to run the applets).Īt the time he proposed his radical hypothesis, Planck could not explain why energies should be quantized. ![]() You can get a feel for this by clicking on the black body applet from PHeT below. The result is a maximum in the plot of intensity of emitted radiation versus wavelength, as shown in Figure 2.2.2, and a shift in the position of the maximum to lower wavelength (higher frequency) with increasing temperature. At any temperature, however, it is simply more probable for an object to lose energy by emitting a large number of lower-energy quanta than a single very high-energy quantum that corresponds to ultraviolet radiation. ![]() As the temperature of an object increases, there is an increased probability of emitting radiation with higher frequencies, corresponding to higher-energy quanta. We can understand Planck’s explanation of the ultraviolet catastrophe qualitatively as follows: At low temperatures, radiation with only relatively low frequencies is emitted, corresponding to low-energy quanta. By assuming that energy can be emitted by an object only in integral multiples of hν, Planck devised an equation that fit the experimental data shown in Figure 2.2.2. \]Īs the frequency of electromagnetic radiation increases, the magnitude of the associated quantum of radiant energy increases. ![]()
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