A velocity selector is to be constructed to select ions with a velocity of $6 \mathrm{~km} \mathrm{~s}^{-1}$. If the electric field used is $400 \mathrm{~V} \mathrm{~m}^{-1}$, then the magnetic field to be used is

• A

  $\frac{11}{20} \mathrm{~T}$
• B

  $\frac{2}{3} \mathrm{~T}$
• Correct answer
  C

  $\frac{1}{15} \mathrm{~T}$
• D

  $\frac{2}{15} \mathrm{~T}$

Hence, the correct answer is option: 'C'.