Question

Light of wavelength 5000 Å falls on a metal surface of work function 1.9 eV. Find (a) the energy of photos (b) kinetic energy of photoelectrons?

Answer 1

Wavelength of light (λ)= 5000 Å=5000×10⁻¹⁰=5×10⁻⁷m
Work function (ℎv)=1.9eV =1.9×1.6×10⁻¹⁹J=3.04×10⁻¹⁹ J

Energy of photons 

E=ℎv=ℎc/λ=6.626×10⁻³⁴×3×1085×10⁻⁷=3.97×10⁻¹⁹ J
Kinetic energy of photoelectrons =ℎv−ℎv=3.97×10⁻¹⁹−3.04×10⁻¹⁹ =9.3×10⁻²⁰J