Luminous infrared radiation

• A. Penetrates more deeply into tissues with high wattage
• B. Has a wavelength range of 1500-12,000 mu
• C. Has tungsten filaments as a source
• D. Has a longer wavelength than nonluminous infrared radiation

Answer: (C)

Luminous infrared radiation is infrared energy emitted by a hot object that also emits visible light. Tungsten filaments are a classic source because when they are heated they glow visibly and also radiate infrared energy. That makes tungsten filaments the best descriptor for luminous infrared radiation.

The other statements don’t define luminous IR accurately: the specified wavelength range isn’t the standard characteristic of luminous IR, because luminous infrared can span a broad mix of wavelengths and isn’t fixed to that window; tissue penetration depends more on wavelength and tissue properties than simply on having higher wattage; and the distinction between luminous and nonluminous infrared isn’t about one type always having longer wavelengths than the other, since both can cover overlapping IR ranges and the defining feature is the presence or absence of visible light together with the infrared.