1Physics 117Physics 117.3Lecture 13Wed 15 June 2016Physics 117Today’s Scheduled Topics•§27.2 –The Photoelectric Effect andthe Particle Theory of Light•§27.3 –X-Rays•§27.5 –The Compton Effect•§28.1 –Early Models of the Atom•§28.2 –Atomic Spectra•§28.3 –The Bohr ModelPhysics 117Planck’s Hypothesis•En= nhf where:–nis an integer;–fis the oscillation frequency (and the frequency of the emitted electromagnetic wave);–his Planck’s constant = 6.626 ×10-34J·s•Planck’s Hypothesis plays a role in explaining the photoelectric effect.Physics 117Photoelectric Effect•When light is incident on certain metallic surfaces, electrons are emitted from the surface.–This is called the photoelectric effect.–The emitted electrons are called photoelectrons.•The effect was first discovered by Hertz.•The successful explanation of the effect was given by Einstein in 1905.Physics 117Fig. 27-4, p. 914The photoelectric effect can be studied using this setup:Physics 117Fig. 27-5, p. 914
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