Final answer:
The intensity of the laser increases the number of photons, leading to more electrons being ejected from the photo tube, thus increasing the current; however, it does not directly increase the voltage, which is determined by the frequency of the photons.
Step-by-step explanation:
The intensity of a laser does indeed affect the voltage across the photo tube. When the intensity of the laser light increases, more photons hit the surface of the photo tube. This results in a greater number of electrons being ejected, which in turn increases the current. However, this increase in light intensity doesn't increase the voltage directly, as the voltage across the photo tube is determined by the energy of the individual photons, which is related to their frequency, not their intensity. Consequently, while increased intensity might lead to more electrons being ejected, only a change in frequency (and thus the energy of the photons) would alter the maximum kinetic energy of the ejected electrons, affecting the voltage.