The threshold wavelength for a metal of work -function W₀ is $\lambda$₀ The threshold wavelength
for a metal having work-function 3 Wo will be

• A

  ${\mathrm{\lambda }}_0$

• B

  ${\mathrm{\lambda }}_0/2$

• C

  ${\mathrm{\lambda }}_0/3$

• D

  ${\lambda }_0/4$