What characteristic describes infra-red radiation?

Infra-red radiation is characterized as being invisible to the human eye and can be felt as warmth when it interacts with the skin. This form of radiation is part of the electromagnetic spectrum, situated between visible light and microwaves. Although infra-red radiation cannot be seen, it plays a crucial role in various applications, including therapeutic practices in beauty and wellness, where its heating effects are utilized for muscle relaxation, pain relief, and improving circulation.

The correct characterization emphasizes the sensory experience associated with infra-red radiation, specifically that it generates a heat sensation without being visually perceptible. Hence, this distinction lays the foundation for understanding the practical uses of infra-red in various therapeutic contexts, affirming its significance in both beauty treatments and medical applications.