Photoelectric Effect...
Ill write down a model answer if you must have one:
"The debate about the true nature of light was "resolved" when Loius de Broglie proposed the wave-particle duality theory. The photoelectric effect demonstrates the particle like properties of light.
If we assumed a wave model, the observations seen could not be explained. We know that the energy of a wave is proportional to the intensity. Therefore, increasing the intensity should increase the kinetic energy of the particles released. But this is not seen. What is seen is that MORE photoelectrons of the SAME kinetic energy are released.
Also, waves transfer energy continuously. If a light wave continuously transmitted energy to a metal, eventually the electrons would gain enough energy to escape the metal. Thus the frequency would not matter. However, this is not the case and electrons are not emitted below a certain threshold frequency.
A particle model of light can explain these observations. If we assume light is made up of particles known as photons (quanta of EM radiation) that have a discrete amount of energy denoted by E = hf. We can see that by increasing the frequency we increase the energy of a photon. And thus by increasing the frequency, the SAME number of photoelectrons are released but of a higher kinetic energy. Because one photon interacts with only one electron, the energy is transmitted and a higher KE of the photoelectrons is seen.
Every metal has a work function - the minimum amount of energy required to JUST cause photoemission. If the energy of photons is not greater than the work function, no photoemission occurs. Because E is proportional to f, below a certain frequency the photons dont have enough energy to cause photoemission."
Haha that was good revision
