A point source of light produces photoelectrons from a photo cell with certain velocity. Which of the following is correct for the photoelectrons if the distance between the photo cell and the source of light is increased?
Choose one answer.
a. Velocity will increase.
b. Velocity will decrease.
c. Velocity will remain the same.
d. Number of photo electrons will increase.
To understand what happens to the photoelectrons when the distance between the photo cell and the source of light is increased, we can refer to the principles of photoelectric effect.
The photoelectric effect is the phenomenon where electrons are emitted from a material when it absorbs photons with sufficient energy. The energy of the photons is related to their frequency (or wavelength) through Planck's equation: E = hf, where E is the energy of the photon, h is Planck's constant, and f is the frequency of the photon.
When a photon reaches the surface of a material, it can transfer its energy to one of the electrons in the material. If the energy of the photon exceeds the work function of the material (the energy required to remove an electron from the material), the electron can be ejected from the material and become a photoelectron.
Now, let's consider the scenario in question. If the distance between the photo cell and the source of light is increased, the intensity of the light reaching the photo cell decreases. This means that fewer photons will be reaching the photo cell per unit time. As a result, the number of photoelectrons emitted from the photo cell will decrease (Option d is incorrect).
However, the energy of each photon and the velocity of the photoelectrons remain unaffected by the distance between the photo cell and the source of light. The energy of a photon is determined by its frequency, which remains constant as long as the light source does not change. Similarly, the velocity of the photoelectrons depends on the specific material and the energy of the photons, rather than the distance between the photo cell and the light source.
Therefore, the correct answer is c. The velocity of the photoelectrons will remain the same when the distance between the photo cell and the source of light is increased.