If $$\lambda$$_Cu is the wavelength of K_$$\alpha$$ X-ray line of copper (atomic number 29) and $$\lambda$$_Mo is the wavelength of the K_$$\alpha$$ X-ray line of molybdenum (atomic number 42), then the ratio $$\lambda$$_Cu/$$\lambda$$_Mo is close to

A metal surface is illuminated by light of two different wavelengths 248 nm and 310 nm. The maximum speeds of the photoelectrons corresponding to these wavelengths are u₁ and u₂, respectively. If the ratio u₁ : u₂ = 2 : 1 and hc = 1240 eV nm, the work function of the metal is nearly