The ratio of wavelengths of proton and deuteron accelerated by potential \( V_p \) and \( V_d \) is \( 1:\sqrt{2} \). Then, the ratio of \( V_p \) to \( V_d \) will be:
\( 1:1 \)
\( \sqrt{2}:1 \)
\( 2:1 \)
\( 4:1 \)