Final answer:
Increasing the frequency of light while maintaining intensity constant will increase the photoelectric effect by causing the ejected electrons to move faster. The number of electrons ejected stays the same, as intensity, which defines the number of photons, is constant.
Step-by-step explanation:
When light is projected onto a semi-conductive surface, and the intensity is held constant while the frequency of light is increased, then the photoelectric effect will also increase.
This is because, according to the equation E = hv, where E is the energy of the photons, and v is the frequency of the light, the energy of the photons increases with frequency. Once the frequency is equal to or higher than the threshold frequency, which is the minimum frequency required to eject electrons, the electrons will be ejected. As the frequency increases beyond the threshold, the ejected electrons will move faster, although the number of electrons ejected will remain the same if the intensity is constant.
Therefore, the correct answer to what happens when the frequency of light projected onto a semi-conductive surface is increased, while keeping the intensity constant, is (b) the photoelectric effect will increase, with the rate at which the electrons are being ejected will increase.