Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Infrared light is light with the longest wavelengths and lowest frequencies. You can't see infrared light, but you can feel it as heat. Besides the sun, flames and living things give off infrared light. Answer: infrared light
Output:
What type of light can you feel as heat but not see and has the longest wavelengths and lowest frequencies?