Two identical photocathodes receive light of frequencies $\mathrm{f}_1$ and $\mathrm{f}_2$. If the velocities of the photo electrons (of mass $\mathrm{m}$ ) coming out are respectively $\mathrm{v}_1$ and $\mathrm{v}_2$, then

• Correct answer
  A

  $v_1^2-v_2^2=\frac{2 h}{m}\left(f_1-f_2\right)$
• B

  $v_1+v_2=\left[\frac{2 h}{m}\left(f_1+f_2\right)\right]^{1 / 2}$
• C

  $v_1^2+v_2^2=\frac{2 h}{m}\left(f_1+f_2\right)$
• D

  $\mathrm{v}_1-\mathrm{v}_2=\left[\frac{2 h}{\mathrm{~m}}\left(\mathrm{f}_1-\mathrm{f}_2\right)\right]^{1 / 2}$

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