where does the light energy of a glowing light wand come from
The glow stick contains two chemicals and a suitable dye (sensitizer, or fluorophor). This creates an exothermic reaction. The chemicals inside the plastic tube are a mixture of the dye and diphenyl oxalate. The chemical in the glass vial is hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place, yielding two moles of phenol and one mole of peroxyacid ester (1, 2-dioxetanedione). The peroxyacid decomposes spontaneously to carbon dioxide, releasing energy that excites the dye, which then relaxes by releasing a photon. The wavelength of the photon -- the color of the emitted light -- depends on the structure of the dye. The reaction releases energy mostly as light, with very little heat. The reason for this is that the reverse 2 + 2 photocycloaddition of 1, 2-dioxetanedione is a forbidden transition (it violates Woodward -- Hoffmann rules) and cannot proceed through a regular thermal mechanism.