(5%) Problem 6: In a photoelectric effect experiment you illuminate a metal with
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(5%) Problem 6: In a photoelectric effect experiment you illuminate a metal with light of an unknown wavelength and measure the maximum kinetic energy of the photoelectrons to be 0.45 eV. Then you illuminate the same metal with light of a wavelength known to be 2/3 of the first wavelength and measure a maximum kinetic energy of 2.5 eV for the photoelectrons. > 50% Part (a) Find the first wavelength, in nanometers. Grade Summary Deductions Potential 100% sinO cotan asin( tan() acosO cos) Submissions Attempts remaining: 6 (0% per attempt) detailed view atan0 acotan0 sinh0 cosh0 tanh cotanh0 0% Degrees Radians VO Submit Hint I give up! Hints: 2% deduction per hint. Hints remaining: 4 Feedback: 2% deduction per feedback. 50% Part (b) Find the metal's work function, in electron volts.Explanation / Answer
6. given
wavelength = lambda
KE = 0.45 eV
walvength 2 = 2*lambda/3
KE2 = 2.5 eV
a. hence let the work functino of the metal be phi
hc/e*lambda = phi + 0.45 eV
hc/e*lambda2 = phi + 2.5
hc/e ( 1/lambda - 1/lamdba2) = -2.05
6.62*10^34*3*10^8 / 1.6*10^-19 ( 3/2*lambda - 1/lambda) = 2.05
lambda = 302.7439 nm
b. phi = hc/e*lambda - 0.45 = 3.65 eV
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