If the energy of photon is 25ev and work function of the material is 7ev then find the value of stooping potential.

To find the stopping potential when you have a photon energy of 25 eV and a work function of 7 eV, we can use the photoelectric effect principles. The stopping potential is the voltage needed to stop the emitted photoelectrons from reaching the anode in a photoelectric experiment. Let's break this down step by step.

Understanding Photon Energy and Work Function

The energy of a photon is the energy it carries, which in this case is given as 25 eV. The work function (φ) of a material is the minimum energy required to remove an electron from the surface of that material, which here is 7 eV. When a photon strikes the material, it can transfer its energy to an electron. If the photon energy exceeds the work function, the electron is emitted.

Calculating the Kinetic Energy of Emitted Electrons

When the photon energy is greater than the work function, the excess energy is converted into the kinetic energy (KE) of the emitted electrons. The relationship can be expressed as:

• Kinetic Energy (KE) = Photon Energy (E) - Work Function (φ)

Substituting the values:

• KE = 25 eV - 7 eV = 18 eV

Relating Kinetic Energy to Stopping Potential

The stopping potential (V_s) is the potential difference required to stop the electrons with this kinetic energy. The relationship between kinetic energy and stopping potential is given by the equation:

• KE = e * V_s

Here, e is the charge of an electron, which is approximately 1 eV per volt. Therefore, we can express the stopping potential as:

• V_s = KE / e

Since we are working in electron volts, we can directly use the kinetic energy value:

• V_s = 18 eV / 1 = 18 V

Final Result

The stopping potential required to halt the emitted electrons is therefore 18 volts. This means that if you apply a potential difference of 18 volts in the opposite direction, it will prevent the electrons from reaching the anode.

In summary, by understanding the relationship between photon energy, work function, and kinetic energy, we can effectively determine the stopping potential in a photoelectric experiment. This concept is crucial in fields such as quantum mechanics and materials science, where the behavior of electrons under various conditions is studied.