Some people do not appreciate the practical importance of Quantum Mechanics, considering it nothing more than some calculations and ideas in the pages of a book. Of course, the man-created digital electronics era would not be possible without an understanding of QM but also, as it turns out, certain everyday natural phenomena are possible due to the quantum characteristics of our world. One these natural phenomena is plant photosynthesis.
That interesting way plants use to convert sunlight into their fuel wouldn't be possible without the quantum-mechanical properties of the world. The main idea is very similar to what happens in photoabsorption of semiconductors, in which a photon of the right energy excites an electron into the conduction band. However, the multiple excitations and availability of states makes the process complicated. This is just another example of how simple models (energy and forbidden bands) have implication in many different fields and/or situations.
Photosynthetic processes have a nearly 100% efficiency. So, if we can ever control/mimic the way plants do photosynthesis we'll have, to name one example, highly efficient solar fuel cells.
For the mean time, we'll have to keep admiring nature and its quantum mechanical ways!
2 hours ago