Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Infrared light can pass right through objects that stop visible light entirely. In the image on the left you can't see the man's hands at all - the plastic bag stops the visible light from passing through. In the infrared image on the right, taken with an infrared camera sensitive from 7.5 - 13 microns, the bag seems to disappear, and his hands are visible. But just like infrared light can get through some things that visible light doesn't, it's also stopped by some things that let visible light through. Notice the eyeglasses in both images. In infrared light, they're completely opaque.