Final answer:
All objects emit radiation if they have a temperature above absolute zero (-273.15°C or 0 K). This includes objects at very low temperatures which emit low-energy electromagnetic radiation. The spectrum and intensity of the radiation depend on the object's temperature.
Step-by-step explanation:
All things emit radiation, provided that their temperature is above absolute zero. The concept of absolute zero is defined as the temperature at which all molecular motion has ceased, which is -273.15°C or 0 K. Even objects at low temperatures emit some form of electromagnetic radiation, although the spectrum and intensity vary with temperature. Stars, for example, are often compared to a blackbody, an idealized object that radiates electromagnetic waves when heated, with absorption and radiation in balance.
To observe different temperatures and their corresponding emissions:
- A star with a temperature of 5800 K typically emits visible light.
- A gas heated to one million K would emit X-rays.
- A person on a dark night emits infrared radiation, which is detectable with thermal imaging equipment.
The danger of exposure to different types of electromagnetic radiation, such as X-rays versus radio waves, is due to their different energies; X-rays have much higher energy and can damage biological tissues, whereas radio waves have lower energy and are generally considered safe.