1. Blackbody is a body,that absorbs all radiation that incident upon him and re-radiates the energy.The emitted radiation usually consists of infrared,ultraviolet,light which all produce heating effect.
2. Cool blackbody emits mostly long wavelengths (microwave or infrared). As they heat up, blackbodies radiate more high energy (short wavelength) ultraviolet emissions.
3. When heated,a solid object will glows and emits thermal radiation/ heat.As the temperature arises,the object becomes red,then yellow,and then white.
4. The wavelength of the hottest (white) has shortest wavelength compared to yellow and red.The yellow has shorter wavelength compared to red.
5. The higher the temperature of a black body,the more energy is emitted
6. Earth’s surface behave approximately as black body.
7. Example,if earth has temperature = 288 K,hence E = (5.67x10¯⁸ watt m¯²K¯⁴)( 288 )⁴.Hence,the radiation emitted by earth is,390 watt m¯²
8. Most objects emit radiation at many wavelength.However,there is one wavelength where an object emits the largest amount of wavelength.This wavelength can be found by using wein’s law,ᵞmax (lambda max) = 2897 µm / T(K).
9. Example,the maximum wavelength does the earth emits =10.0 µm
10.A practical black body can be constructed by making a box,with perfectly reflected EMR material within it,and then has a small hole on its surface.
11.Radiation that enters through the hole will be trapped inside the box.The hole absorbs radiation just like a black body.
12.The various wavelength of radiation emitted by a black body depend only on its temperature.
Point of ponder :
What happens if the input energy > output energy?The object will become warmer
What happens if the input energy > output energy?The object will become warmer
What happens if the input energy < output energy?The object will become cooler
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