Electrons are accelerated through a potential difference $V$ and protons are accelerated through a potential difference $4V$. The de-Broglie wavelengths are $\lambda_e$ and $\lambda_p$ for electrons and protons respectively. The ratio of $\frac{\lambda_e}{\lambda_p}$ is given by: (given $m_e$ is the mass of the electron and $m_p$ is the mass of the proton).

• A
  $\frac{\lambda_e}{\lambda_p} = \sqrt{\frac{m_p}{m_e}}$
• B
  $\frac{\lambda_e}{\lambda_p} = \sqrt{\frac{m_e}{m_p}}$
• C
  $\frac{\lambda_e}{\lambda_p} = \frac{1}{2}\sqrt{\frac{m_e}{m_p}}$
• D
  $\frac{\lambda_e}{\lambda_p} = 2\sqrt{\frac{m_p}{m_e}}$