5. Blackbody Radiation Hot objects glow (toaster coils, light bulbs, the sun). As the temperature increases the color shifts from Red (700 nm) to Blue (400 nm) The classical physics prediction was completely wrong! (It said that an infinite amount of energy should be radiated by an object at finite temperature)
6. Blackbody Radiation Spectrum Visible Light: ~0.4 m to 0.7 m Higher temperature: peak intensity at shorter Wien’s Displacement Law: max T = 2.898x10 -3 m·K
7. Blackbody Radiation: First evidence for Q.M. Max Planck found he could explain these curves if he assumed that electromagnetic energy was radiated in discrete chunks , rather than continuously. The “quanta” of electromagnetic energy is called the photon. Energy carried by a single photon is E = hf = hc / Planck’s constant: h = 6.626 x 10 -34 Joule sec
8. Preflights 22.1, 22.3 A series of light bulbs are colored red, yellow, and blue. Which bulb emits photons with the most energy? The least energy? Which is hotter? (1) stove burner glowing red (2) stove burner glowing orange
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17. Young’s Double Slit w/ electron Screen a distance L from slits Source of monoenergetic electrons L Jönsson – 1961 d 2 slits-separated by d
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19. Young’s Double Slit w/ electron Source of monoenergetic electrons L Merli – 1974 Tonomura – 1989 Same pattern for photons One electron at a time Interference pattern = probability d
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Notas do Editor
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Note humans are ‘hot’ 300K so we emit light, just not much in the visible spectrum. Try infrared.
Note humans are ‘hot’ 300K so we emit light, just not much in the visible spectrum. Try infrared. Classical theory at 3000 k: ultraviolet catastrophe (see p. 985 text)
Note humans are ‘hot’ 300K so we emit light, just not much in the visible spectrum. Try infrared.
greater intensity increases current does not change maximum KE
higher frequency light increases max. KE Below threshold freq, no current Electrons emitted immediately, no delay as “energy is accumulated”
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