Quantum Theory, Work Funciton

In summary, the question is asking for the least energy that could result in photoelectron production if the work function is 3.00 eV. The equation used is KE = E - W, where KE is the kinetic energy, E is the energy of the photon, and W is the work function. The answer is that the energy must be larger than the work function, so the least energy of the given options would be 3.50 eV.
  • #1
sgoeke
14
0

Homework Statement



Of the following energies for photons, which is the least energy that could result in photoeletron production if the work function is 3.00 eV?
a. 1.50 eV
b. 2.90 eV
c. 3.50 eV
d. 6.01 eV

Homework Equations



KE = E - W

The Attempt at a Solution



I don't know where to go with this. please help!
 
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  • #2
sgoeke said:
KE = E - W
What do the three terms in this equation stand for? Which ones can be identified with what is given?
 
  • #3
KE is the kinetic energy, E is the energy of the photon (E=hf or E=hc/lambda), and W is the work function. 3 eV is the work function (W). We're looking for E. But I don't know what KE would be.
 
  • #4
sgoeke said:
KE is the kinetic energy, E is the energy of the photon (E=hf or E=hc/lambda), and W is the work function. 3 eV is the work function (W). We're looking for E. But I don't know what KE would be.
No you don't. Go down the list of possible answers starting with (a). Would a 1.50 eV photon produce a photoelectron? If so, what would would the photoelectron's KE be?
 
  • #5
How do you know you produce a photoelectron?
 
  • #6
sgoeke said:
How do you know you produce a photoelectron?
Can a 1.50 eV photon produce a photoelectron if the work function is 3.0 eV? The answer is "yes" or "no". If you don't know how to answer this question then you do not understand the photoelectric effect, specifically what "work function" means. You need to review the photoelectric effect by reading your textbook or getting on the web. If you are still confused, explain what you do understand and what you don't and someone will help you.
 
  • #7
The KE depends on the light frequency and the critical frequency is the photons whose energy is equal to the work funciton. I guess I'm really not making the connection for this problem even after reading this section of my textbook multiple times.
 
  • #8
The idea behind the photoelectric effect is very simple. Think of energy as money. The work function is the exit fee that an electron has to pay to leave the metal. A photon comes along and gives all the money it has to an electron in the metal. Two things may happen as a result.
1. If the electron has more money than the exit fee, it pays it, leaves the metal and takes with it the change as kinetic energy.
2. If the electron does not have enough money to pay the exit fee, it stays where it is and the photon's money is shared in some fashion within the metal.

Now again, can you answer the question "Can a 1.50 eV photon produce a photoelectron if the work function is 3.0 eV?"
 
  • #9
So the energy would need to be larger than the work function? So the least amount of energy for the ones given would be 3.5?
 
  • #10
sgoeke said:
So the energy would need to be larger than the work function? So the least amount of energy for the ones given would be 3.5?
Bingo! :biggrin:
 
  • #11
Thanks...that really really helped!
 

1. What is quantum theory?

Quantum theory, also known as quantum mechanics, is a scientific framework that explains the behavior of particles at the atomic and subatomic level. It describes how particles can exist in multiple states simultaneously and how they interact with each other through the exchange of energy.

2. What is the work function in quantum theory?

The work function in quantum theory refers to the minimum amount of energy required to remove an electron from a material's surface. It is a fundamental concept in understanding the photoelectric effect and plays a crucial role in the behavior of electrons in electronic devices.

3. How does the work function affect electron movement?

The work function determines the energy level at which electrons can move freely within a material. If the energy of an incoming photon is greater than the work function, the electron will be emitted from the material. If the energy is lower, the electron will remain bound to the material.

4. Can the work function be altered?

Yes, the work function can be altered by changing the material's properties, such as its composition or surface conditions. It can also be changed by applying an external electric field to the material.

5. What are some practical applications of quantum theory and the work function?

Quantum theory and the work function have numerous practical applications, including the development of electronic devices such as transistors, solar cells, and LEDs. They are also essential in understanding and manipulating chemical reactions and materials at the nanoscale, which has implications in fields such as medicine and energy production.

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