I was reading about cyclotron and it's working. I found out that electrons cannot be accelerated by this device. The reason I found was that they are too light. But I want to know why exactly electron having mass(9.1*10^-31 kg) cannot be accelerated?
They can, but being light, they speed up with very little energy. This is when the cyclotron will stop being useful, since its frequency has to be tuned to the mass of the accelerated particle. Very soon, relativistic effects will become important (let's say that the apparent, or effective, mass will grow) and the cyclotron will be out of tune, unable to give more energy to the electron. You then obtain electrons with little energy, not very interesting.