What is the work function of the metal if the light of wavelength 4000Å generates photo electrons of velocity 6 × 105ms⁻¹ from it?
(Mass ofelectron = 9 × 10⁻³¹kg, Velocity of light = 3 × 10⁸ ms⁻¹, Planck's constant = 6.626 × 10⁻³⁴ Js, Charge of electron = 1.6 × 10⁻¹⁹JeV⁻¹)
(1) 0.9eV
(2) 2.1eV
(3) 3.1eV
(4) 4.0eV