What is the number of photons of light with a wavelngth of ` 400 p m` that provide ` 1 J ` of energy ?

Explanation

`E_("photon")=hv=(hc)/lambda=(6.625xx10^(-34) J sxx3.00xx10^(8) m s^(-1))/(4000xx10^(-12) m)`
`=4.9687xx10^(-17) J`
Number of photons that provide
`1` joule of energy `=1.00/(4.9687xx10^(-17))=2.012xx10^(16)` photons