HW Question 1.33

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Phoebe Chen 4I
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Joined: Fri Sep 28, 2018 12:29 am

HW Question 1.33

Postby Phoebe Chen 4I » Mon Oct 15, 2018 4:26 pm

I am unsure how to get the wavelength value for part c of questions 1.33. What I did is take the required frequency of 2.50x10^16 Hz and divided c by that to get wavelength. But my wavelength value did not match the answer.
Screen Shot 2018-10-15 at 4.24.06 PM.png

Tam To 1B
Posts: 72
Joined: Fri Sep 28, 2018 12:25 am

Re: HW Question 1.33

Postby Tam To 1B » Mon Oct 15, 2018 5:55 pm

Part c asks you to find the wavelength of the energy of the photon. In this case, you would use the equation E(photon) - work function = E(kinetic energy), where E(photon) = work function + E(kinetic energy).
So from part b you should have found the work function to be 1.66E-17 J. Convert the given velocity they give you from km to m so 3.6E3kms^-1 --> 3.6E6ms^-1. Now to find the E(kinetic energy), you use the formula E(kinetic energy) = (1/2)mv^2 = (1/2)(9.11E-31kg)(3.6E6ms^-1)^2 to get 5.90E-18 J. Add this value with the work function to get your E(photon) = 2.25E-17 J. Then you use this energy value to plug it into the formula for wavelength (E = hc/λ --> λ = hc/E) to get 8.8E-9 m, or 8.8 nm.

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