Final answer:
Doubling the photon flux of light increases the number of photons hitting the metal's surface, leading to more electrons being ejected if the light's frequency is above the metal's threshold frequency. This increase does not affect the kinetic energy of the electrons, which is dependent on the light's frequency, not its photon flux. So the correct option is A.
Step-by-step explanation:
The effect of doubling the photon flux of light on whether electrons will be emitted from metal ties into the concept known as the photoelectric effect. The photon flux relates to the number of photons hitting a specific area in a given time and is associated with the intensity of the light. According to the photoelectric effect, the kinetic energy of the emitted electrons is directly proportional to the frequency of the incident light and not the intensity, assuming the frequency is above the metal's threshold frequency. However, the number of emitted electrons is indeed proportional to the intensity of the light, which is determined by the photon flux.
If the frequency of the light is kept constant but the intensity (photon flux) is increased by doubling the amount of light, more photons would strike the metal's surface, resulting in more electrons being ejected if the frequency is above the metal's threshold frequency. Hence, options (B) and (D) do not accurately describe the outcome, as the velocity (kinetic energy) of the ejected electrons is unaffected by the increase in number of photons, and photon flux certainly affects electron emission as long as the frequency is above the threshold. Since the number of collisions with photons would increase with brighter light, the number of ejected electrons increases. Therefore, (C) is also incorrect because whether or not electrons are emitted is not time-dependent but instead depends on the frequencies and intensities involved.