Why does light striking a metal surface eject only electrons, not protons?
I suppose two reasons. One is that the electrons are on the outside of an atom which makes them much more accessible than the protons which are located in the nucleus. Second, the protons are much more massive than the electron and the kinetic energy required to eject a proton is so much larger than that required to eject an electron.
When light strikes a metal surface, it can cause the ejection of electrons, a phenomenon known as the photoelectric effect. This is because electrons in the metal gain enough energy from the incoming photons of light to overcome the attractive forces holding them within the metal. However, protons, which are found in the nucleus of an atom, are not ejected during this process. This is due to a few reasons:
1. Relative mass: Electrons have a much smaller mass compared to protons. Electrons are roughly 1,800 times lighter than protons. This difference in mass affects the ease with which they can be ejected from the metal surface by the energy from incoming photons.
2. Binding forces: The electrons in an atom are loosely held compared to protons and neutrons in the nucleus. Protons are bound by the strong nuclear force, which is significantly stronger than the forces holding electrons in the atomic shell. As a result, protons are less likely to be affected by the energy from incident light.
3. Lack of charge: Protons have a positive charge, whereas electrons have a negative charge. When light interacts with matter, it typically interacts with the negatively charged electrons due to their relatively weaker binding forces and their ability to move more freely within the material. Protons, being positively charged, are less likely to be affected by the electric fields associated with photons of light.
Overall, the combination of the smaller mass, weaker binding forces, and absence of a significant charge on the protons contributes to the photoelectric effect mainly ejecting electrons rather than protons when light strikes a metal surface.
The phenomenon you're referring to is known as the photoelectric effect. When light strikes a metal surface, it can release electrons from the metal. This happens because light is made up of particles called photons, which carry energy.
To understand why only electrons are ejected and not protons, we need to consider the nature of atoms. Atoms consist of a central nucleus made up of protons and neutrons, with orbiting electrons. The protons in the nucleus have a positive charge, while the electrons have a negative charge.
When light shines on a metal surface, one or more photons can be absorbed by the atoms present. For electrons to be ejected, the photons need to have enough energy to overcome the attractive force between the electrons and the positively charged nucleus.
The key factor here is the difference in mass between protons and electrons. Protons are roughly 1,840 times more massive than electrons. As a result, photons with enough energy to overcome the attractive force will transfer their energy to the electrons, allowing them to escape the metal's surface.
On the other hand, protons are much heavier than electrons and wouldn't be easily displaced by the energy of the photons. Therefore, only electrons are ejected during the photoelectric effect.