What is stopping potential
.pls describe with full details
.pls describe with full details
Definition
The stopping potential is defined as the potential necessary to stop any electron (or, in other words, to stop even the electron with the most kinetic energy) from reaching the other side.
What happens in photoelectric effect is that, an incident radiation strikes the surface of the metal. Now, as the incident photons with a certain energy, strike the surface of the metal, they transfer their energy to the electrons in the outer shell of the metal atom so that they ionize and come out of the metal atom. This is called emission and this happens only when the incident photon strikes with sufficient energy. The energy should be sufficient for the electron to be able to come out of the metal atom. However, the energy that this electron receives may either be exactly the same amount as required by it or it may be of some amount which is slightly greater than what is required. In the latter case (lets say case 2), the electron uses the extra amount of energy as its kinetic energy and thus gains some speed. However in the former case (lets say case 1), the electrons are just emitted but they gain no speed. The entire amount of energy is used in the emission. So, in the tube, if the photocurrent is to be detected, the requirement is that some current flows through the circuit. For this, electrons must flow. And for that, electrons should gain some speed.
Explaining stopping potential
When we apply a positive potential on the plate placed directly opposite to this metal plate, the plate attracts the negative electrons. A force acts on these electrons and thus they get accelerated towards this plate. So, the more positive potential we apply on this (collector) plate, more rapidly will the electrons flow through the circuit. But if we apply a negative potential on this (collector) plate, the electrons will not approach so easily. Only the electrons with sufficient energy and hence, velocity, will be able to surpass this opposing potential called retarding potential of the (collector) plate. If we keep on increasing this negative (retarding) potential, there will be one point when no more electrons reach this plate and thus, no electron flows through the circuit. Thus, current flow through the circuit stops. This potential applied on the (collector) plate is called as the stopping potential.
Definition
The stopping potential is defined as the potential necessary to stop any electron (or, in other words, to stop even the electron with the most kinetic energy) from reaching the other side.
What happens in photoelectric effect is that, an incident radiation strikes the surface of the metal. Now, as the incident photons with a certain energy, strike the surface of the metal, they transfer their energy to the electrons in the outer shell of the metal atom so that they ionize and come out of the metal atom. This is called emission and this happens only when the incident photon strikes with sufficient energy. The energy should be sufficient for the electron to be able to come out of the metal atom. However, the energy that this electron receives may either be exactly the same amount as required by it or it may be of some amount which is slightly greater than what is required. In the latter case (lets say case 2), the electron uses the extra amount of energy as its kinetic energy and thus gains some speed. However in the former case (lets say case 1), the electrons are just emitted but they gain no speed. The entire amount of energy is used in the emission. So, in the tube, if the photocurrent is to be detected, the requirement is that some current flows through the circuit. For this, electrons must flow. And for that, electrons should gain some speed.
Explaining stopping potential
When we apply a positive potential on the plate placed directly opposite to this metal plate, the plate attracts the negative electrons. A force acts on these electrons and thus they get accelerated towards this plate. So, the more positive potential we apply on this (collector) plate, more rapidly will the electrons flow through the circuit. But if we apply a negative potential on this (collector) plate, the electrons will not approach so easily. Only the electrons with sufficient energy and hence, velocity, will be able to surpass this opposing potential called retarding potential of the (collector) plate. If we keep on increasing this negative (retarding) potential, there will be one point when no more electrons reach this plate and thus, no electron flows through the circuit. Thus, current flow through the circuit stops. This potential applied on the (collector) plate is called as the stopping potential.
