In this iit jee physics lectures, we are going to talk about the electron, photon, and the photoelectric effect. In the above IIT JEE physics video, we are going to learn the following topics e/m of an electron, charge on an electron, and emission of an electron.

So let’s begin with e/m for an electron. After the discovery of the electron, J.J.Thomson had found out the value of e/m value of an electron, which is the charge to mass ratio. In his experiment, the e/m value was found to be 1.759x1011C/Kg. Similarly one can find the e/m ratios for other particles too. Further, we discussed charge on an electron. The charge on an electron was found out by a very famous experiment call the Milliken’s oil drop experiment. He had studied the motion of the oil drop in air. Suppose we have taken the charge as q1, q2, q3. The values of q1, q2, q3 were found to be integer multiples and hence he had taken the HCF and had found out the electron charge. He has used the value e/m which was proposed by Thomson, and Mullikan found out the mass of an electron which was 9.1X10-31kg. The electronic charge was denoted by ‘e’ and its value was 1.6×10-19kg.

In the end, we have discussed the photoelectric metal. By now you know that the surface of metal is a sea of electrons where ions are static. So how does the emission of electrons take place? There are three emissions;

1. Thermionic emission: It was used in dyad walls in earlier days. On heating the metal, electron emission takes place. Due to heating of metal, the electrons gain energy and come out of the metal.
2. Field emission
3. Secondary emission.

All this we study before any chapter in physical chemistry for iit jee. 