Another quantum-optical phenomena

Planck s hypothesis was confirmed and developed by Einstein s theory of an external photo-effect. 

In this expression, work A is nndetermined since it is not known at precisely what point of the cathode body the collision took place. The work A2 is a characteristic of every metal and oxide and is referred to as work function. If we exclude the unknown term from this line, i.e., remove the term A1, the equation become valid only for those electrons which, at the moment of collision, were on the surface of electrode A they have the highest possible kinetic energy. Therefore  

It is possible to determine the kinetic energy of the photoelectron using the experimental value of the locking out voltage. Then we can write  

It follows from this equation that there is a limiting frequency coj. below which the photo-effect in a given photocathode disappears completely. In fact, the quantum ho does not have enough energy to tear an electron out of the surface of electrode C. This happens when hco is lower than the work function. The so-called photo-electric threshold takes place at ho = A2. 

In addition to the theory of an IBB, it has been proved in quite another experiment that, in some circumstances, light behaves as a particle flux rather than a wave. 

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