Certain sum glasses having small of `AgCl` incroporated the lenses, on expousure to light of appropriate wavelength turns to gray colour to reduce the glare following the reactions:
`AgCloverset(hv)(rarr) Ag("Gray")+Cl`
If the heat of reaction for the decomposition of `AgCl` is `248 kJ mol^(-1)`, what maximum wavelength is needed to induce the desired process?

Explanation

Energy needed to change `=248xx10^(3) J//mol`
If photons is used for this purpose, then according to Einstein law one molecule absorbs one photon.
Therefore, `:. N_(A).(hc)/(lambda)=248xx10^(3)`
`lambda=(6.626xx10^(-34)xx3.0xx10^(8)xx6.023xx10^(23))/(248xx10^(3))=4.83xx10^(-7) m`