Another Photoelectric effect problem

In summary, the conversation discusses the calculation of the stopping potential in a photoelectric-effect experiment using the equations 1/2 m_e v_max^2=hf- ϕ and v_max=eV_stop. The question arises whether to use the electron rest mass value or to multiply it by the number of electrons in sodium, and the relationship between the work function and cutoff frequency is mentioned.
  • #1
creativepinky
3
0

Homework Statement



In a photoelectric-effect experiment, light of wavelength (x) nm is incident on a sample of sodium. The work function of sodium is (y) J. Calculate the stopping potential required to just stop all electrons from reaching the anode.

Homework Equations



To work out frequency, I've used taken c= λ ×f, therefore f= c/λ
which can now be put into:

1/2 m_e v_max^2=hf- ϕ

(which can then be used in the equation v_max=eV_stop to work out the stopping potential.)

The Attempt at a Solution



My question is do you take the value for the electron rest mass (m_e) as 9.109 x 10^-31 to calculate this or do you need to multiply this by the number of electrons that are within sodium (11) and then use this for the value of m_e?

Many thanks in anticipation.
 
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  • #2
creativepinky said:

Homework Statement



In a photoelectric-effect experiment, light of wavelength (x) nm is incident on a sample of sodium. The work function of sodium is (y) J. Calculate the stopping potential required to just stop all electrons from reaching the anode.

Homework Equations



To work out frequency, I've used taken c= λ ×f, therefore f= c/λ
which can now be put into:

1/2 m_e v_max^2=hf- ϕ

(which can then be used in the equation v_max=eV_stop to work out the stopping potential.)

The Attempt at a Solution



My question is do you take the value for the electron rest mass (m_e) as 9.109 x 10^-31 to calculate this or do you need to multiply this by the number of electrons that are within sodium (11) and then use this for the value of m_e?

Many thanks in anticipation.

You mean [tex] KE_{max} = eV_{stop} [/tex] right? If you multiplied by 11 wouldn't that mean the individual photon released 11 electrons from the atom? Do you even need to use [tex] m_e [/tex]?
 
  • #3
K.E max =eVstop = h(f-f0)=hc/λ - y (Work function)

where f is freq, f0 is cutoff freq

the work function (y) can be related
f0 = y/h = c/λ0


hope that helps
 

1. How does the photoelectric effect work?

The photoelectric effect is a phenomenon where electrons are emitted from the surface of a material when it is exposed to light. This occurs because the light energy is absorbed by the material, causing the electrons to gain enough energy to overcome the binding forces holding them in the material.

2. What factors affect the photoelectric effect?

The photoelectric effect is affected by the intensity, frequency, and wavelength of the incident light, as well as the type of material and its surface properties. Increasing the intensity of the light or using a higher frequency or shorter wavelength can increase the number of photoelectrons emitted.

3. How is the photoelectric effect related to the quantum nature of light?

The photoelectric effect provided evidence for the quantum nature of light, as it showed that light is composed of discrete packets of energy called photons. The energy of a photon is directly proportional to its frequency, and only photons with enough energy can cause the photoelectric effect to occur.

4. Can the photoelectric effect be explained by classical physics?

No, the photoelectric effect cannot be explained by classical physics. According to classical physics, increasing the intensity of light should increase the kinetic energy of the emitted electrons, but this is not observed in experiments. The photoelectric effect can only be explained by the particle-like nature of light proposed by quantum mechanics.

5. What are the practical applications of the photoelectric effect?

The photoelectric effect has many practical applications, including solar panels, photocells, and photomultiplier tubes. It is also used in devices such as photocopiers, barcode scanners, and digital cameras. Understanding the photoelectric effect also led to the development of the field of quantum mechanics, which has numerous applications in modern technology.

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