Light is shone on a metal and photoelectrons are emitted, what are the three things which might cause the photoelectron emission to stop
The three things that might cause photoelectron emission to stop when light is shone on a metal are:
1. Decrease in the intensity (brightness) of the incident light: When the intensity of the incident light decreases, fewer photons are incident on the metal surface. As a result, the number of photoelectrons emitted decreases, eventually leading to the emission stopping completely.
2. Insufficient energy of the incident photons: The photoelectric effect occurs when the energy of the incident photons is equal to or greater than the work function of the metal. The work function is the minimum energy required to remove an electron from the metal surface. If the energy of the photons is lower than the work function, the electrons cannot be ejected, and the emission will stop. Changing the wavelength or frequency of the light can alter the energy of the incident photons.
3. Saturation of the surface: When photoelectrons are emitted, they create a negative charge on the metal surface. This negative charge can repel further incoming photons, making it more difficult for additional electrons to be emitted. Eventually, the surface becomes saturated, and the emission stops due to the repulsion between emitted electrons and incident photons.
To determine whether any of these factors could cause the photoelectron emission to stop, you can experimentally vary the intensity of the incident light, change the wavelength/frequency of the light, or observe the behavior of the emission over time to check for saturation effects.