Photoelectric effect and intensity What changes occur to the maximum kinetic energy of an emitted electron from the surface of a metal if the intensity of a laser incident to the surface is reduced
 A: No changes occur. The photoelectric effect consists of interactions of one photon and one electron. The kinetic energy transmitted to the electron originates solely in the energy of the photon, which is a function only of the light's frequency
$E = \hbar \nu $
Changing the intensity only modifies the amount of photons which are going to impact the surface. Therefore, changing the intensity has no impact to the maximum kinetic energy of the emitted electrons.
A: If by intensity you mean number of photons, then there is no change in the max KE.
If you mean the colour of the laser is changed such that each photon has a smaller energy (also reduces intensity as power is reduced), then the electrons will be emitted with smaller KE.
A: The kinetic energy of the emitted electron is given by $E_{k} = E_{\gamma} - E_{B}$, where $E_{\gamma}$ is the energy of the incident photon and $E_{B}$ is the binding energy of the electron. The energy of a photon depends on its frequency, $E_{\gamma} = h\nu$, and hence reducing the intensity of the incident light does not affect the maximum kinetic energy of the emitted electron.
A: The photoelectric effect means ejecting electron using photon.
1 photons gives the energy to 1 electron.
So if number of photon that is intensity increases number of electron ejected increases.
But if energy of photon that is frequency increases then the energy per electron ejected that is kinetic energy increases.
It is a simple notion if you think light is made of particle. But you can't explain if you think light is made of waves.
1 particle like 1 bullet injures 1 person that is emits 1 electron. More bullets or higher intensity of bullets and more injuries. More energy per bullet or more frequency per photon and more lethal injury.
so intensity is related to no. And frequency is related to energy.
Simple concept but none other than Einstein could explain this. Nor hertz neither Planck.
Simple yet complex
A: photoelectric effect proposed by Einstein has been proved by experiments and is well accepted.  
The theory of Photoelectric effect states: light can be viewed as particles . One photon carries 1 hv where v is the frequency.
The kinetic energy gained by an electron is thus a function of frequency only and has nothing to do with how many photons present.
Thus reducing the laser's intensity will NOT change the kinetic energy of the ejected electron.
A: The maximum KE of the ejected electron depends on the energy of the photon that strikes the metal. 
The number of electrons that are ejected depends on the number of photons that strike the surface in concern.
This is a common misconception, higher intensity does not correspond to higher energy. Visually, the intensity of light corresponds to its brightness, and this is dependent on the number of photons that are in the region in concern. The energy of light visually corresponds to its colour, you can pull up a visual spectrum diagram, and the energy of light increases from the red end to the blue end of the spectrum.
So, if the intensity is reduced, the number of electrons ejected per unit area decreases, but their maximum KE stays the same.
