A metal plate gets heated, when cathode rays strike against, it due to

In Thomson experiment of finding $e/m$ for electrons, beam of electron is replaced by that of muons (particle with same charge as of electrons but mass $208$ times that of electrons). No deflection condition in this case satisfied if

Who produced electromagnetic waves for the first time ? 

An electron beam is moving between two parallel plates having electric field $1.125 \times {10^{ – 6}}N/m$. A magnetic field $3 \times {10^{ – 10}}T$ is also applied so that beam of electrons do not deflect. The velocity of the electron is ………… $m/s$

The colour of the positive column in a gas discharge tube depends on