Final answer:
The stopping potential in the photoelectric effect is related to the energy of the incident light. By rearranging the equations and plugging in the given values, we can calculate the charge of the photoelectron. The charge of the photoelectron corresponds to the charge of an electron, indicating that the cathode is made of metal.
Step-by-step explanation:
The stopping potential, in the photoelectric effect, is the minimum potential difference that prevents the photoelectrons from reaching the anode. This stopping potential is related to the energy of the incident light photons using the equation:
E = qV
where E is the energy of the photons, q is the charge of the photoelectron, and V is the stopping potential. Rearranging the equation, we have:
V = E/q
The energy of a photon can be calculated using 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. Substituting these values, we have:
V = (hc/λ)/q
Given that the stopping potential is 2.20 V and the wavelength is 192 nm (or 1.92 x 10^-7 m), we can calculate the charge of the photoelectron:
q = (hc/λ)/V
Plugging in the values, we get:
q = (6.626 x 10^-34 J s * 3 x 10^8 m/s)/(1.92 x 10^-7 m * 2.20 V)
simplifying:
q ≈ 9.034 x 10^-19 C
This value corresponds to the charge of an electron, which indicates that the cathode is made of metal.