Quantum Physics: Work Function and Electric Potential

In summary, a metal surface with a work function of 3.0eV and an electric potential 5V lower than infinity is illuminated with 200nm wavelength light. The maximum kinetic energy of the emitted photoelectrons can be determined using the equation K.Emax= hf - Φ, where f=c/λ. However, to accurately calculate the maximum kinetic energy, the impact of the electric potential must also be taken into account. This would cause the maximum kinetic energy of the photoelectrons to increase, as they would be attracted to the metal surface and require more energy to escape. To find the energy required to escape the surface, the work function must be converted from eV to joules.
  • #1
JohnGaltis
18
0

Homework Statement


Metal Surface is illuminated with 200nm wavelength light. Work Function of this metal is 3.0eV and its electric potential is 5V lower than a point of infinity.

Determine max K.E of photoelectrons, which are just emitted from the work surface.

Homework Equations


K.Emax= hf - Φ
f=c/λ
Not sure what other equations.

The Attempt at a Solution


I found f first by using f=c/λ. This way, I got a value of max K.E. But it's a really high mark question so it got to be more than just subbing in values.

I think I haven't yet include the impact the electric potential would have on the photoelectrons. It would cause the max K.E of photoelectrons to increase, right? Since it would be attracted to the metal surface and would need more energy to escape.

What equation would allow me to find the energy required to escape the surface?
 
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  • #2
Show your calculations. did you convert eV into joules?
 

1. What is the work function in quantum physics?

The work function in quantum physics refers to the minimum amount of energy required to remove an electron from a metal surface. This energy is necessary to overcome the attractive forces of the positively charged nucleus and the negatively charged electron.

2. How is the work function related to the electric potential?

The work function is directly related to the electric potential through the equation W = qV, where W is the work function, q is the charge of the electron, and V is the electric potential. This means that the work function is proportional to the electric potential.

3. What factors affect the work function of a material?

The work function of a material is primarily affected by the type of material and its surface properties. Metals generally have lower work functions compared to non-metals due to their abundance of free electrons. Additionally, the temperature and irradiation of a material can also affect its work function.

4. How does the work function play a role in the photoelectric effect?

The photoelectric effect is the phenomenon where electrons are emitted from a metal surface when light is shone on it. The work function is crucial in this process as it determines the minimum energy of the incident light required to remove an electron from the metal surface. If the energy of the light is lower than the work function, no electrons will be emitted.

5. Can the work function of a material be changed?

Yes, the work function of a material can be changed by altering its surface properties or by applying an external electric field. This can be useful in various applications, such as in photovoltaic cells where the work function of a material is modified to efficiently collect and convert light energy into electricity.

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