Could in fared rays have their frequency reduced and turned into light rays?
Well, yes, it can be done. As everybody said, you need to increase the frequency (or reduce the wavelength) to make infrared (not “in fared”) become visible light. As one person said, infrared goggle measure infrared light and then use electronics to make a visible image. So that is something that can be done. However, there are a series of techniques that do change infrared light into visible light by increasing the frequency. The two most common techniques (the only ones I can think of) are frequency doubling and sum-frequency generation. These are roughly analogous to frequency doubling and mixing for electric signals. One person said that visible light is higher energy than infrared, so you need to add energy to do this. This is correct. But in frequency doubling and sum-frequency generation, two infrared photons are combined to create one visible photon. This process conserves energy. This type of interaction happens only in very specialized materials. There needs to be a non-line
