Light therapy does not typically use which part of the spectrum?

• A. Ultraviolet
• B. Infrared
• C. Visible light
• D. Microwave

Answer: (A)

Light therapy relies on specific wavelengths of light to influence bodily processes such as mood, circadian rhythm, or tissue healing. The wavelengths typically used fall within the visible spectrum, and sometimes near-infrared light is included when deeper penetration is desired. Ultraviolet light is not typically used because it carries enough energy to damage DNA, increase skin cancer risk, cause photoaging, and harm the eyes with overexposure. For safety and efficacy, therapeutic devices focus on visible wavelengths and, when helpful, near-infrared, avoiding UV exposure. Microwave energy isn’t part of the light spectrum at all, so it isn’t used in light therapy.