Light energy, effects

Navarro RM, Valle F, Fierro JLG (2008) Photocatalytic hydrogen evolution from CdS-ZnO-CdO systems under visible light irradiation Effect of thermal treatment and presence of Pt and Ru cocatalysts. Int J Hydrogen Energy 33 4265-4273... 

When electrons fall to lower energy levels, light is given off. What energy effect is expected when an electron jumps to a higher energy orbit ... 

At illuminated p-type semiconductors, light energy brings about a shift of the applied cathode potential at which C02 reduction takes place toward a less negative potential by the photovoltaic effect.94 Thus, light energy can be used to reduce the apparent overpotential of C02 reduction. 

Is the UV-stabilization only due to the screening effect (or more precisely light absorbing effect in a spectral region where the absorption spectra of polymer and UV-stabilizer overlap) of the UV-stabilizers and/or can it be enhanced by an energy transfer from the excited polymer to the stabilizer molecule ... 

With increasing concentration of DHB, the photoproduct forms more slowly, as evidenced by decreasing loss of fluorescence intensity (Table I, entries 1-3). Nevertheless, the concentration of photoproduct(s) and RET from the polymer to photoproduct(s) are expected to increase with time, and stabilization of the polymer will eventually depend upon the capability of the photoproduct(s) to dissipate excitation energy imparted in the RET process. The observed decrease in stabilization efficiency by DHB (based on film discoloration) with exposure time in an accelerometer indicates that DHB is more effective than the photoproduct(s) in dissipating the light energy. Similar spectroscopic studies on polystyrene have led to the same conclusion in this case, as well.6... 

Plants developed from photosynthetic bacteria. As we have explained in Chapters 5 and 6, bacteria could evolve on the top surface of the Earth by increasing their ability to capture light (energy) and by obtaining and using more effectively 15-20 elements from seawater, later the seabed and land, and with three or four from the atmosphere, while utilising novel chemistry. The need to adapt to oxygen later forced the development of compartments already seen in differentiated ... 

Furthermore, the magnitude of the energy in this answer helps explains why we sometimes wish to employ light to effect a reaction, because a chemical reagent simply does not possess enough energy (see later examples). 

---