Photoelectric Experiment: Stopping Potential Calculation

Introduction:
In a photoelectric experiment, light is incident on a photocathode, and the emitted electrons are collected at an anode. The stopping potential refers to the minimum potential required to prevent the emitted electrons from reaching the anode. In this experiment, the wavelength of the incident light is 500 nm, and the work function of the photocathode is 1.5 eV. We need to determine the stopping potential.

Working Principle:
The photoelectric effect occurs when photons of sufficient energy strike a material, causing the emission of electrons. The energy of a photon is given by the equation E = hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength of the incident light. If the energy of a photon is greater than or equal to the work function of the material, electrons will be emitted.

Step 1: Calculate the Energy of the Incident Light:
Using the equation E = hc/λ, we can calculate the energy of the incident light. Plugging in the values, we get:
E = (6.626 x 10^-34 J.s * 3 x 10^8 m/s) / (500 x 10^-9 m)
E ≈ 3.97 x 10^-19 J

Step 2: Convert Energy to Electron Volts:
Since the work function is given in electron volts (eV), we need to convert the energy to eV. Using the conversion factor 1 eV = 1.6 x 10^-19 J, we find:
E ≈ 3.97 x 10^-19 J / (1.6 x 10^-19 J/eV)
E ≈ 2.48 eV

Step 3: Calculate the Stopping Potential:
The stopping potential (V_s) is equal to the difference between the energy of the incident light (E) and the work function (φ). Therefore, we have:
V_s = E - φ
V_s = 2.48 eV - 1.5 eV
V_s ≈ 0.98 eV

Conclusion:
The stopping potential in this photoelectric experiment is approximately 0.98 eV. This means that a potential of 0.98 volts needs to be applied in the opposite direction of the emitted electrons to prevent them from reaching the anode.