Photons of wavelength `lambda` are made incident on sample of diatomic gas `X_(2)`. If bond energy of `X-X` bond is `EkJ mol^(-1)`:
(a) Find critical value of `'lambda'` so as break `X-X` bond
(b) Assuming photons posses more energy than required to break the `X-X` bond, what X-then would be the KE per `X(g)` atom after the bond is broken ?

Explanation

(a)` (hc)/(lambda) = E_(photon)`
One photon breaks implies one bond.
Energy to break one bond `=(E(1000))/(N_(A))J`.
Condition to break bond
`(hc)/(lambda)ge(1000E)/(N_(A))`
`implies lambdale(hcN_(A))/(1000E)`
(b) The energy balance equation is
`E_("photon") = E_("Bond") +2KE_(H)`
Where `E_(Bond)` = energy to break 1 bond
`KE_(H)` = KE of each H-atom
`implies(1)/(2)((hc)/(lambda)-(1000E)/(N_(A))) = KE_(H)`