更新1:
so shiny metals emits more readily?
更新2:
And dull metals are good absorber but bad emitters? THanks.
Ability to emit EM wave
2008-06-11 3:12 am
In my testbook, it says if the surface of a substance is dull then it is poor in emitting infrared and if it is shiny, then the opposite. But why? Shiny appearance makes light to bound off the substance, therefore making it hard to absorb it and emit it. And dull surfaces on the other hand should be easy to absorb light because it doesn't bound off it. So why saying dull surfaces are bad emitters of infrared? Or UV? Or visible light? Or EM waves? THanks!!!
回答 (2)
2008-06-18 7:51 pm
✔ 最佳答案
No. There should be something wrong with your textbook or you have misinterpreted what it says.By the [black body radiation principle], a body which is a good absorber of thermal radiation is also a good emitter of thermal radiation, and vice versa.
Dull surface objects absorb more thermal radiation than shiny surface objects and is, therefore, a good emitter of thermal radiation than shiny surface objects.
You may refer to the following web-pages:
http://www.newton.dep.anl.gov/askasci/phy00/phy00134.htm
http://209.85.175.104/search?q=cache:kq9v4VXDMuIJ:heattransferprojects.wikispaces.com/space/showimage/chan+enlin.ppt "thermal radiation"+"dull surface"&hl=zh-TW&ct=clnk&cd=14&gl=hk
2008-06-11 3:27 am
因為absorb 左, 唔會放番出黎, so it is bad emitter
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