Question

Light of wavelength 5000 A° falls on a sensitive surface .If the surface has received 10 ^-7 J energy,how many photos have fallen on the surface?
ans:-25×10^10

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