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Physics 6C Ch28worksheet Solutions

# Physics 6C Ch28worksheet Solutions - PHYSICS 6C Ch.28...

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PHYSICS 6C Ch.28 Worksheet Solutions clas.ucsb.edu/staff/vince/ 1) A flashlight emits 1.5W of power. Assuming a frequency of 5.2x10 14 Hz for the light, determine the number of photons given off per second. The energy of each photon is given by E=hf, or E=(6.63x10 -34 J-s)(5.2x10 14 Hz)=3.45x10 -19 J Dividing 1.5W by this energy gives 4.4x10 18 photons per second. 2) The work function of gold is 4.58 eV. What frequency of light must be used to eject electrons from a gold surface with a maximum kinetic energy of 6.48x10 -19 J? Is this light visible to the human eye? Converting to Joules, (4.58eV)(1.6x10 -19 J/eV)=7.33x10 -19 J This is the energy necessary to just barely eject the electrons from gold. We need to add the extra kinetic energy to get the energy of the photon. E photon =1.38x10 -18 J. The frequency is given by E=hf. f photon =2.1x10 15 Hz This light is in the ultraviolet range of the spectrum and cannot be seen by humans. 3) Find the wavelength of the photon required to excite a hydrogen atom from the n=2 state to the n=5 state.

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Physics 6C Ch28worksheet Solutions - PHYSICS 6C Ch.28...

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