Finding Penetration Depth in a finite well

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Homework Help Overview

The problem involves a 50-eV electron trapped between capacitors charged to 200V, with the goal of determining how far the electron's wave function extends beyond the capacitors. The original poster expresses difficulty in reaching the known answer of 1.6 x 10^-11 m.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the relationship between the potential energy and the voltage of the capacitors, questioning the need to multiply the voltage by the elementary charge to find the potential energy. Other participants engage in clarifying the intent behind the original poster's inquiries and offer support.

Discussion Status

The discussion includes attempts to clarify concepts related to potential energy and voltage. Some participants express a willingness to assist and explore the problem collaboratively, indicating a supportive environment for further exploration.

Contextual Notes

The original poster mentions uncertainty regarding the steps taken to arrive at the answer, particularly in the context of understanding the physics behind the calculations. There is an acknowledgment of the need for clarification on the relationship between voltage and potential energy.

JasonZ
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The problem is as follows:

A 50-eV electron is trapped between negligible-width capacitors charged to 200V (each with an exit hole). How far does its wave function extend beyond the capacitors? I know the answer is 1.6 x 10^-11 m, but I cannot get to that.

Any ideas?

-Jason
 
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A person who is clever than you is only a few pages ahead in the manual, simply read the manual, so you won't have to ask twice...
 
Hey,

I am not sure if you were trying to come off as rude, but that's how it sure seems. By manual I assume you mean the text I am getting my problem from? If that's the case, I have read the chapter on my own, as well as looked over the section this problem is from several times and I can't get it. Supposing I am not as clever as you, perhaps you could give me a useful hint, rather than condescend.

*Edit*

I managed to come to the correct answer, though I am not sure why exactly my last step worked. Apparently I had to multiply the 200V, and the 50 eV by the elementary charge (e). I understand why I multiplied 50 eV by e, but can somene explain why I needed to multiply 200 V, by e? I think it has to do with 200 V being the potential difference across the capacitors, whereas I need the Potential Energy. I am not fresh on E&M, can someone verify that step as correct?

Thank you,
-Jason
 
Last edited:
Jason, I too am new to PF, and meant no offence.

Its not users like myself you have to be worried about, its the PF monitors.

They don't mind if you show how you tried to solve a problem, everyone is willing to advise and assist...

What are you studying and look it up myself, to see if I can find us an answer for us both.

Regards

Terry
 

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