AP Chemistry chapter six question NEED HELP!!!?

the stratospheric ozone (O3) layer helps us protect us from harmful ultraviolet radiation. it does so by absorbing ultraviolet light and falling apart into an o2 molecule and Oxygen atom , a process known as photodissociation. O3(g)= O2 (g) + O2(g) Use the data in appendix C to calculate the enthalpy change for this reaction. What is the maximum wavelength a photon can have if it is to possess sufficient energy to cause this dissociation? In what portion of the spectrum does this wavelength occur?