There are some waves we cannot see. Water can absorb them, and begin to oscillate at the same frequency. You can see this for yourself if you put a glass of water on something very flat and very still. Give it a few hours, and you should see tiny waves in the water. The longer you wait, the bigger the ripples.
You can make your own solar cell. Easiest way is to harvest a lot of yellow flowers. Soak them in some vinegar overnight (you can get it at a grocery store). Then put in about 3 ounces of baking soda and stir. If you have done it correctly, you should see some foam. Harvest this foam and place between 2 sheets of glass or plastic. Attach 2 wires and point it at the sun. Voila, homemade solar cell.