Discussion Forum

A metal surface is illuminated by light of two different wavelengths 248nm and 310 nm. The maximum speed of the photoelectrons corresponding to these wavelengths are u1  and u₂, respectively. If the ratio u1:u₂=2:1 and hc=1240 eV n m, the work  function of the meal  is nearby

Answer:

Explanation:

Energy corresponding to 248 nm wavelength

               $= \frac{1240}{248}eV=5eV$

 Energy corresponding to 310 nm wavelength

$= \frac{1240}{310}eV=4eV$

                $= \frac{KE_{1}}{KE_{2}}=\frac{\mu_1^2}{\mu_2^2}=\frac{4}{1}$

                               =  $\frac{5eV-W}{4eV-W}$

  $\Rightarrow$          $16-4W=5-W$

$\Rightarrow$        11=3W

 $\Rightarrow$       $W=\frac{11}{3}=3.67 eV \cong 3.7eV$