Photochromic sunglasses, which darken when exposed to light, contain a small amount of colorless AgCl embedded in the glass. When irradiated with light, metallic silver atoms are produced and the glass darkens: AgCl→Ag+Cl. Escape of the chlorine atoms is prevented by the rigid structure of the glass, and the reaction therefore reverses as soon as the light is removed.If 310 kJ/mol of energy is required to make the reaction proceed, what wavelength of light is necessary?