1. (noun) the infrared region of the electromagnetic spectrum; electromagnetic wave frequencies below the visible range

• infrared frequency

2. (noun) electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves

• infrared emission
• infrared light
• infrared radiation

1. (noun) the infrared region of the electromagnetic spectrum; electromagnetic wave frequencies below the visible range

• frequence
• frequency
• oftenness

2. (noun) electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves

• actinic radiation
• actinic ray

1. (adjective) having or employing wavelengths longer than light but shorter than radio waves; lying outside the visible spectrum at its red end

• invisible
• unseeable