Final answer:
The photoelectric effect experiment measures the stopping potential, the voltage needed to stop photoelectrons, which is constant for a given light frequency regardless of intensity.
Step-by-step explanation:
The Photoelectric Effect and Stopping Potential
In the photoelectric effect experiment, if the potential difference between the anode and cathode is equal to the stopping potential, no photocurrent would flow. This occurs because the stopping potential is the minimum voltage required to counter and halt the flow of photoelectrons from the cathode to the anode. A characteristic of the photoelectric effect is that the value of the stopping potential is constant for a given frequency of incident light regardless of its intensity. Therefore, the stopping potential is fundamentally tied to the energy of the ejected electrons, which is determined by the energy of the incident photons minus the work function of the metal.
Experimental setups for observing the photoelectric effect feature an evacuated tube with a cathode illuminated by monochromatic light to emit photoelectrons, and an anode to collect them, measuring the resultant photocurrent. The potential difference can be adjusted to find the stopping potential, which, as signified in the setup, has a value (for example, 0.17 V) where the photocurrent ceases.