KVPY2020ChemistryStructure of Atom
A certain metal has a work function of Φ = 2 eV . It is irradiated first with 1   W of 400 nm light and later with 1   W of 800 nm light. Among the following, the correct statement is: [Given:Planck constant h = 6 . 626 × 10 - 34   m 2 kgs - 1 Speed of light ( c ) = 3 × 10 8   ms - 1 ]
Options
- ABoth colors of light give rise to same number of photoelectrons.
- B400 nm light gives rise to less energetic photoelectrons than 800 nm light.
- C400 nm light leads to more photoelectrons.
- D800 nm light leads to more photoelectrons.
Correct answer
C. 400 nm light leads to more photoelectrons.
Step-by-step solution
Work function of metal ϕ = 2 eV Energy of photon λ = 400 nm = hc λ = 3 . 105 eV Energy of photon λ = 800 nm = hc λ = 1 . 5525 eV Hence, photon with λ = 400 nm will emit photoelectrons while photon with λ = 800 nm will not emit photoelectrons.