Question

Photons of energies 1 eV and 2.5 eV are incident on a metal surface of work function 0.5 eV. Then the ratio of maximum velocities with which the photoelectrons are emitted being

• A. 1 : 4
• B. 4 : 1
• C. 2 : 1
• D. 1 : 2

Answer 1

Answer: (D)

1 : 2

From, $\frac{1}{2}m{v}^2=E-\phi$
${\left(\frac{V_1}{V_2}\right)}^2=\frac{E_1-\phi }{E_2-\phi }$
${\left(\frac{V_1}{V_2}\right)}^2=\frac{0.5}{2}$
$\frac{V_1}{V_2}=\frac{1}{2}$

So, the answer is option (D).