Cathode rays are

Cathode rays are similar to visible light rays in that

What is the speed of cathode rays?

$A$ metallic surface with a work function of $2 \, eV$,on heating to a temperature of $800 \, K$,gives an emission current of $1 \, mA$. If another metallic surface having the same surface area,same emission constant,but a work function of $4 \, eV$ is heated to a temperature of $1600 \, K$,then the emission current will be......$mA$.

The thermionic emission of electrons is due to:

In $1897$,$J$.$J$. Thomson discovered which particle?