Achieve #7

[Tianna Nguyen 1I]

Hi, I don't understand how to solve the second part of #7:
"Suppose the typical work function of the metal is roughly 4.720×10^−19 J. Calculate the maximum wavelength in angstroms of the radiation that will eject electrons from the metal.
Considering that microwave ovens radiate at 2.45 GHz, how would you respond to the debate?"
I got 4.204 x 10^3 Å for the first part. How do I use this number to solve the second part?

[Brian Diehl 2B]

Hey Tianna!

To answer the second question, you would actually need to compare the energy value of the work function to the energy of the microwave's radiation corresponding to its frequency of 2.45 GHz. Your Angstrom calculation in the first part won't come into play :)

[Tianna Nguyen 1I]

Hey Tianna!

To answer the second question, you would actually need to compare the energy value of the work function to the energy of the microwave's radiation corresponding to its frequency of 2.45 GHz. Your Angstrom calculation in the first part won't come into play :)

Thanks for answering! Could you elaborate on how to compare the values? Do I need to do some sort of conversion?

[Brian Diehl 2B]

Hey Tianna!

To answer the second question, you would actually need to compare the energy value of the work function to the energy of the microwave's radiation corresponding to its frequency of 2.45 GHz. Your Angstrom calculation in the first part won't come into play :)

Thanks for answering! Could you elaborate on how to compare the values? Do I need to do some sort of conversion?

Hey again! Sorry for the late response.

We know that in order for an electron to be emitted from the metal's surface, the energy of the incoming photon must be greater than or equal to the energy needed to remove the electron (aka the work function/threshold energy). The approach I had in mind was using the given radiation frequency of 2.45 GHz to calculate the photon energy using the formula E_photon=hv. Next, I would compare this energy value to the given work function 4.720×10^-19 J. If this value is greater than the work function, then I would know that the energy of the microwave's radiation could be overcoming the threshold energy, thus the emission of electrons may be due to the photoelectric effect. If this value was smaller than the work function, then I would know that the emission of electrons cannot be due to the photoelectric effect.

I also apologize for the poor wording on my end in the last post; the Angstrom calculation in part 1 CAN be used to make a comparison that would answer the debate. Since 4.204 x 10^3 Å is the maximum wavelength that can eject electrons from the metal's surface, the wavelength of the microwave's radiation must be less than or equal to this value in order for electrons to be emitted. You would find this value by converting 2.45 GHz to wavelength using the formula c=λv, and then you can make the judgment on whether or not the photoelectric effect could be a possible causation from there. I just decided against using this method in case my Angstrom calculation ended up being wrong.

Hope this brought you some clarification!