Question

What is the number of photons of light with wavelength 4000 pm which provide 1 Joule of energy ?

Answer 1

Energy of photon (E) `=(hc)/(lambda)`
`h=6.626 xx 10^(-34)Js, c=310^(8) ms^(-1), lambda=4000 xx10^(-12) =4xx10^(-9)m`
`:. " " "Energy of photon" (E)=((6.626 xx10^(-34)Js)xx(3xx10^(8)m s^(-1)))/((4xx10^(-9)m))=4.969 xx 10^(-17)J`
Now, `4.965 xx 10^(-17)J` is the energy of photon =1
`:. 1 J ` is energy of photons `=(1)/(4.969 xx10^(-17))=2.012 xx 10^(16)` photons.