1B.15

Cecilia Cisneros 1F
Posts: 121
Joined: Wed Sep 30, 2020 9:45 pm

1B.15

1B.15 The velocity of an electron that is emitted from a metallic surface by a photon is 3.6×10^3km⋅s−1. (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 2.50×10^16Hz. 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 am having trouble with part b of this problem because it asks how much energy is required to remove an electron from the metal surface, so I solved for the work function. However, in the solutions manual they solved for the energy of the photon? Why is that? I thought work function = energy needed to remove an electron.

Racquel Fox 2I
Posts: 62
Joined: Wed Sep 30, 2020 10:11 pm

Re: 1B.15

I think you would use the E=hv equation because it's referring to the radiation. The way I interpreted that was that it was asking more specifically about the photon, and I'm pretty sure if the question refers to the photon you would use E=hv rather than any other energy equations.

Posts: 73
Joined: Wed Sep 30, 2020 9:40 pm

Re: 1B.15

Yes, the work function is the energy needed to remove an electron. However, for an electron to be removed, the work function must be greater than or equal to the energy of the photon. Therefore, finding the energy of the photon would give you the minimum energy needed to remove an electron, which is the work function.

tamara masri_3D
Posts: 52
Joined: Wed Sep 30, 2020 9:35 pm
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Re: 1B.15

Hello! In this case, the energy of the photon and the work function should be the same. When the photon reaches a certain energy, it is able to eject the electron with no kinetic energy, which defines the work function as well. Therefore, in this case, the energy needed to remove an electron is coming from the photon, so it would make sense to solve for its energy. Hope this helps!