Homework Problem #33

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Sophia Diaz - Dis 1B
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Homework Problem #33

Postby Sophia Diaz - Dis 1B » Sun Apr 22, 2018 12:58 pm

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km/s
a) What is the wavelength of the ejected electron?
b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 x 10^16 Hz How much energy is required to remove the electron from the metal surface?
c) What is the wavelength of the radiation that caused photoejection of the electron?
d) What kind of electromagnetic radiation was used?

I'm trying to figure out this problem and I just want to make sure I know how to do each of the steps correct. So far:
a) Plug the V into the De Broglie equation then plug that into the Einstein Equation to get the wavelength
b) I'm unsure which equation to use for this, but I think I'm looking for threshold energy?
c) I'm unsure which equation to use for this
d) Using the wavelength of the radiation, look at the spectrum and find out in which light range it fits in

Solene Poulhazan
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Re: Homework Problem #33

Postby Solene Poulhazan » Sun Apr 22, 2018 1:57 pm

I think the equation you are looking for is simply E=hv

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Re: Homework Problem #33

Postby victoriatanaka1C » Sun Apr 22, 2018 2:13 pm

I'm looking for clarification for 1.33 c. When calculating the E required (in order to calculate the wavelength), you have to combine the E required to eject the e- and the energy of ejecting the e-? How do you know when looking at the question that you need to combine both? I originally solved the problem by using my answer from b (the energy required to eject the e-) and plugged it into E = h (c / wavelength) but got way wrong of an answer.

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Re: Homework Problem #33

Postby Chem_Mod » Sun Apr 22, 2018 3:14 pm

You need to use the velocity of the electron given at the top of the problem statement for part c.

Kara Justeson 1B
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Re: Homework Problem #33

Postby Kara Justeson 1B » Sun Apr 22, 2018 9:45 pm

I think for that part you have to use the equation "Ephoton = Ek + work function" based on the correct answer. But I'm also a little confused about this equation and when to use it in general.

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