Final answer:
To calculate the stopping potential for light of a given wavelength falling on potassium, one must use the principles of the photoelectric effect. The energy of the incident photons is determined and the work function of potassium is subtracted to find the kinetic energy of ejected electrons, from which the stopping voltage can be deduced.
Step-by-step explanation:
The student's question involves calculating the stopping potential for potassium when it is exposed to light of a certain wavelength, which falls under the topic of the photoelectric effect in physics.
First, we need to remember that the energy of a photon is given by the equation E = hf, where h is Planck's constant and f is the frequency of the light. The wavelength (λ) and frequency (f) are related by the equation c = λf, where c is the speed of light. Using these equations we can find the energy of the incoming photon.
Once we have the energy of the photon, we subtract the work function of potassium to find the excess energy, which is converted into kinetic energy of the ejected electron. The stopping potential (Vs) is the potential needed to stop the fastest moving photoelectrons, and can be found using the equation eVs = KEmax, where KEmax is the maximum kinetic energy of the photoelectrons, and e is the elementary charge.