Electrons of  1.68×105 J mol-1 kinetic energy are emitted when electromagnetic radiations of 300 nm wavelength fall on Na metal. What is the maximum wavelength of light to exhibit photoelectric effect?

E0=hv0=hv-KE=hcλ-KE      =3.99×10-10J s mol-1×3×108ms-1300×10-19m-1.68×105J mol-1      = 3.99 ×105 -1.68 × 105=2.31 ×105J mol-1 E0=hv0=hcλ0 λ0=hcE0=3.99×10-10Js mol-1×3×108ms-12.31×105 J mol-1=5.18×10-7 m=518 nm