Initially,a photon of wavelength $\lambda_1$ falls on a photocathode and emits an electron of maximum energy $E_1$. If the wavelength of the incident photon is changed to $\lambda_2$,the maximum energy of the electron emitted becomes $E_2$. Then the value of $hc$ ($h=$ Planck's constant,$c=$ velocity of light) is

• A
  $hc = \frac{(E_1 + E_2) \lambda_1 \lambda_2}{\lambda_2 - \lambda_1}$
• B
  $hc = \frac{E_1 - E_2}{\lambda_2 - \lambda_1} \cdot (\lambda_1 \lambda_2)$
• C
  $hc = \frac{(E_1 - E_2)(\lambda_2 - \lambda_1)}{\lambda_1 \lambda_2}$
• D
  $hc = \frac{\lambda_2 - \lambda_1}{\lambda_1 \lambda_2 E_2} \cdot E_1$