The work function for a metal surface is 8.28 eV. The threshold wavelength for this metal surface is :

3 × 10-7 m 2 × 10-6 m 1.5 × 10-7 m 2.8 × 10-6 m

1.5 × 10-7 m

Threshold wavelength of the metal is  $ \lambda = \frac{hc}{\phi} = \frac{6.62\times 10^{-34}\times 3\times 10^8}{8.28\times 1.6\times 10^{-19}}= 1.5\times 10^{-7}m$