We started our investigation of transverse waves with electromagnetic waves...radio, ultraviolet, infrared, visible light, microwaves, gamma waves etc. We tuned analog radios, explored prisms and lenses, and tested our ability to wash our hands thoroughly using "GloGerm" lotion. An IR thermometer can measure the temperature of a surface without actually touching it.
Will putting colored glass over a photocell change the amount of electricity produced? Does the color of the glass matter? At first the children guessed that bluer lighter, higher energy light, would produce more electricity. When this wasn't the case they measured the lumens that passed through each colored piece. It turned out that the blue glass let through much less light than the yellow or orange.