What type of rays are known for their long wavelengths that penetrate the deepest and produce more heat than visible light?

Infrared rays are known for their long wavelengths, which allow them to penetrate deeper into the skin compared to other forms of electromagnetic radiation. This characteristic makes them particularly effective in heating tissues and providing therapeutic benefits, such as improved circulation and muscle relaxation. The deep penetration is due to their longer wavelengths, which can pass through the outer layers of the skin without being absorbed immediately, hence generating more heat compared to visible light or ultraviolet rays.

Ultraviolet rays, while significant in skin treatments and tanning, primarily affect the outer layers of the skin and do not possess the same penetrating ability as infrared rays. X-rays, although they penetrate deeply, are not commonly associated with therapeutic heating effects in esthetics. UVA rays are a subset of ultraviolet light and also lack the depth of penetration that infrared rays offer, focusing more on the outer skin layers rather than providing heating benefits to deeper tissues. Thus, infrared rays stand out for their specific ability to produce deeper heating effects in esthetic treatments.