The photons of light having a wavelength `4000 Å` are necessary to provide `1.00 J` of energy are.

Answer

`2.01 xx 10^(18)` photons

Explanation

Energy of photon,
`E = (hc)/(lambda)`
`:. E = ((6.63 xx 10^(-34) J s) xx (3 xx 10^8 ms^(-1)))/(400 xx 10^(-9) m)`
`= 4.97 xx 10^(-9) m`.
No. of photons in 1J
`= 1/(4.97 xx 10^(-19)) = 2.01 xx 10^(18)` Photons