Quiz 5 Solutions

Quiz 5 Solutions - Physics 1C Fall 2005 Quiz 5 Solutions...

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Physics 1C Fall 2005 Quiz 5 Solutions Version A 1. Blue light ( λ = 460 nm E=hf=2.7eV) is incident on a piece of potassium ( φ = 2.20 eV). What is the maximum kinetic energy of the ejected photoelectrons? ( h = 6.63 × 10 34 J s, c = 3.00 × 10 8 m/s, 1 eV = 1.60 × 10 19 J, and 1 nm = 10 9 m) a. 1.0 eV b. 0.50 eV c. 0.25 eV d. 4.9 eV Max KE electron is E(photon) – work function = 2.7 eV – 2.2 eV = 0.5 eV 2. What is the maximum velocity of a photoelectron emitted from a surface with work function 5.00 eV when illuminated by 200.0 nm ultraviolet light? ( m electron = 9.11 × 10 31 kg, h = 6.63 × 10 34 J s, 1 eV = 1.60 × 10 19 J, and 1 nm = 10 9 m) a. 800 000 m/s b. 653 000 m/s c. 431 000 m/s d. 212 000 m/s E(phot) = hc = 9.9 x 10 -19 J, Wk fn = 5 x 1.6 x 10 -19 J = 8 x 10 -19 J, max KE elec=(9.9-8.0) x 10 -19 J So ½ mv 2 = 1.9 x 10 -19 J, solve for v = 653000 m/s 3. Which change will not change the kinetic energy of the most energetic electrons emitted in the photoelectric effect? a. changing the brightness of the light b. changing the frequency of the light c. changing the metal the light is hitting d. all of the above will change the electron’s kinetic energy
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Quiz 5 Solutions - Physics 1C Fall 2005 Quiz 5 Solutions...

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