Question

The mass of electron moving with velocity of light is:

• A. $2m_e$
• B. $3m_e$
• C. infinite
• D. zero

Answer 1

The correct option is C infinite

As we know,
mass of particle, moving with velocity v is
$m^{{}^{\prime }}$ $=\frac{m}{\sqrt{1-{\left(\frac{v}{c}\right)}^2}}$
so if electron is moving with lights velocity, tthen its mass will be
$m_e^{{}^{\prime }}$ $=\frac{m_e}{\sqrt{1-{\left(\frac{c}{c}\right)}^2}}$
$=\frac{m_e}{\sqrt{1-1}}=1/0=\infty$