what is the number of photons of light with a wavelength of 4000 pm that provide 1 J of energy ?

Explanation

Let N proton of light provide `2J` energy so
`:. E =Nhv= (Nhc)/(lambda)`
or `N = (E lambda)/(hc)`
`= (2 xx 300 xx 10^(-9)m)/(6.262 xx 10^(-34) xx 3 xx 10^(6) ms^(-1))`
`= 3.01 xx 10^(18)` photons