Energy (E) of a photon = hν
Energy `(E_(n))` of ‘n’ photons = nhv
`Rightarrow n=( E_(n)lamda)/(hc)`
Where
`lambda` = wavelength of light = 4000 pm = `4000xx10^(12) m`
c = velocity of light in vacuum = ` 3xx 10^(8)m//s`
h = Planck’s constant = `6.626 xx 10 ^(-34)Js`
Substituting the values in the given expression of n:
`n= ((1)xx(4000xx10^(-12)))/((6.626xx10^(-34)(3 xx 10^(8)))=2.012xx10^(16)`
Hence, the number of photons with a wavelength of 4000 pm and energy of 1 J are `2.012 xx 10^(16)`
