Transcript: The visible spectrum is just one slice of a much larger range of radiations. Nearly two hundred years ago two scientists demonstrated this. Around the year 1800, William Herschel took a spectrum of sunlight and placed a thermometer beyond the red end of the spectrum. The temperature rose, demonstrating that energy existed beyond the visible end of the spectrum. A couple of years later, German chemist Johann Ritter placed a sheet of paper soaked in silver-chloride beyond the blue end of a visible spectrum of sunlight. The paper darkened, also demonstrating that energy existed beyond the blue end of the spectrum. In this way we had proof of infrared radiations beyond the red end of the spectrum and ultraviolet radiation beyond the violet end of the spectrum.