How are the frequency and intensity of incident radiation changed in the experiment of the photoelectric effect?

(N/A) In the photoelectric effect experiment,the frequency and intensity of incident radiation are controlled as follows:
$1$. Frequency: The frequency of the incident radiation is changed by using different light sources or by using filters that allow only specific wavelengths to pass through. Changing the frequency affects the maximum kinetic energy of the emitted photoelectrons.
$2$. Intensity: The intensity of the incident radiation is changed by varying the distance between the light source and the metal surface (using the inverse square law) or by using neutral density filters to reduce the number of photons per unit area per unit time. Changing the intensity affects the number of photoelectrons emitted per second (photoelectric current).