Three properties of infrared radiations similar to the visible light: 1. They travel in straight lines as light does, with a speed equal to 3 x 108 m/s in vacuum. 2. They obey laws of reflection and refraction. 3. They are unaffected by electric and magnetic fields. Two properties of infrared radiation different from the visible light: 1. They are absorbed by glass, but they are not absorbed by rock-salt. 2. They are detected by their heating property using a thermopile or a blackened bulb thermometer.