An $\mathrm{H}$-atom moving with speed $\mathrm{v}$ makes a head-on collision with another $\mathrm{H}$-atom at rest. Both the atoms are in the ground state. The minimum value of velocity $\mathrm{v}$ for which one of the atoms may excite is

• Correct answer
  A

  $\text{6.25}\times {10}^4 \mathrm{m} {\mathrm{s}}^{-1}$
• B

  $\text{8}\times {10}^4 \mathrm{m} {\mathrm{s}}^{-1}$
• C

  $\text{7.25}\times {10}^4 \mathrm{m} {\mathrm{s}}^{-1}$
• D

  $\text{13.6}\times {10}^4 \mathrm{m} {\mathrm{s}}^{-1}$

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