Thermal Radiation
- All bodies (objects), no matter what temperature, emit a spectrum of thermal radiation in the form of electromagnetic waves
- These electromagnetic waves usually lie in the infrared region of the spectrum but could be emitted in the form of visible light or other wavelengths, depending on the temperature
- The hotter object, the more infrared radiation it radiates in a given time
The infrared emitted from a hot object can be detected using a special camera
- The intensity and wavelength distribution of any emitted waves depends on the temperature of the body
- This can be represented on a thermal radiation curve
- As the temperature increases, the peak of the curve moves
- This moves to a lower wavelength and a higher intensity
The peak of a thermal radiation curve moves to the left with increasing temperature
- From the electromagnetic spectrum, waves with a smaller wavelength have higher energy (e.g. UV rays, X-rays)
- When an object gets hotter, the amount of thermal radiation it emits increases
- This increases the energy emitted and therefore the wavelength of the emitted radiation decreases
- At room temperature objects emit thermal radiation in the infrared region of the spectrum
- At around 1000 °C an object will emit a significant amount of red light
- At 6000 °C an object will mainly emit white or blue light (and some ultraviolet)
- At even higher temperatures objects will emit ultraviolet or even X-rays