A metallic surface is illuminated with monochromatic light of wavelength $\mathrm{\lambda }$ and stopping potential for photoelectric current is $5{\mathrm{v}}_{\mathrm{o}}$  when the same metallic surface is illuminated with a light of wavelength $2\mathrm{\lambda }$ , the stopping potential is ${\mathrm{V}}_{\mathrm{o}}$ . What is the threshold wavelength for the surface ?

• A

  $\frac{8\mathrm{\lambda }}{3}$

• B

  $8\mathrm{\lambda }$

• C

  $5\mathrm{\lambda }$

• D

  $3\mathrm{\lambda }$