Question

In a cathode ray tube if V is the potential difference between the cathode and anode, the speed of the electrons, when they reach the anode is proportional to (Assume initial velocity = 0)

• A. $V$
• B. $\frac{1}{V}$
• C. $\sqrt{V}$
• D. $\left(\frac{v^2}{2em}\right)$

Answer 1

The correct option is C $\sqrt{V}$

Here when an electron is accelerated by the potential difference towards the anode then the kinetic energy of electrons is equal to work done by potential on electrons

$\frac{1}{2}m{v}^2=eV$

$v=\sqrt{\frac{2eV}{m}}$

$v=\sqrt{v}$

where e & m are constant

Answer is C.