Question

Monochromatic light of wavelength 4000 Å is incident upon the metallic surface of metals A, B, C having work function 3.4 eV, 4.8 eV and 5.9 eV respectively?[Take, hc = 12,400 eV Å]
1No photoelectrons are emitted from any of metallic surface
2Maximum KE of emitted electrons emitted is 0.3 eV
3If incident wavelength is less than 200 nm, electrons are emitted from all surfaces
4If frequency of incident light is doubled, the maximum kinetic energy is also doubled

Answer 1

$\huge\underline{\boxed{\sf ANSWER}}$

Work function is the minimum energy required by an electron to just escape from the metal surface as to overcome the restraining forces at the surface of metal.

According to Einstein's photoelectric equation the work function of metal is given by :

∴ϕ=$\frac{hc}{λ}$−KE max

ϕ=$\frac{6.6\times 10-34\times 3\times 10^8}{4000 \times 10-10}$-2eV

=3eV−2eV=1eV