Chapter 26. Rate of energy flow in radiation (14-22)

Question

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Question

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{"title":"Rate at which an object emits energy in the form of radiation","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,25,35,70\"}]"} {"title":"Emissivity of the object (a number between 0 and 1)","description":"Correct!","type":"correct","color":"#ffff00","code":"[{\"shape\":\"rect\",\"coords\":\"129,41,157,71\"}]"} {"title":"Temperature of the object on the Kelvin scale","description":"Incorrect","type":"incorrect","color":"#00ff00","code":"[{\"shape\":\"rect\",\"coords\":\"238,25,280,72\"}]"} {"title":"Surface area of the object","description":"Incorrect","type":"incorrect","color":"#ff0000","code":"[{\"shape\":\"rect\",\"coords\":\"200,28,239,72\"}]"} {"title":"Stefan-Boltzmann constant = 5.6704 × 10−8 W . m−2 . K−4","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"159,39,198,72\"}]"}

Question

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{"title":"Rate at which an object emits energy in the form of radiation","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,25,35,70\"}]"} {"title":"Emissivity of the object (a number between 0 and 1)","description":"Wrong","type":"incorrect","color":"#ffff00","code":"[{\"shape\":\"rect\",\"coords\":\"129,41,157,71\"}]"} {"title":"Temperature of the object on the Kelvin scale","description":"Correct!","type":"correct","color":"#00ff00","code":"[{\"shape\":\"rect\",\"coords\":\"238,25,280,72\"}]"} {"title":"Surface area of the object","description":"Incorrect","type":"incorrect","color":"#ff0000","code":"[{\"shape\":\"rect\",\"coords\":\"200,28,239,72\"}]"} {"title":"Stefan-Boltzmann constant = 5.6704 × 10−8 W . m−2 . K−4","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"159,39,198,72\"}]"}

Question

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{"title":"Rate at which an object emits energy in the form of radiation","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,25,35,70\"}]"} {"title":"Emissivity of the object (a number between 0 and 1)","description":"Wrong","type":"incorrect","color":"#ffff00","code":"[{\"shape\":\"rect\",\"coords\":\"129,41,157,71\"}]"} {"title":"Temperature of the object on the Kelvin scale","description":"Incorrect","type":"incorrect","color":"#00ff00","code":"[{\"shape\":\"rect\",\"coords\":\"238,25,280,72\"}]"} {"title":"Surface area of the object","description":"Correct!","type":"correct","color":"#ff0000","code":"[{\"shape\":\"rect\",\"coords\":\"200,28,239,72\"}]"} {"title":"Stefan-Boltzmann constant = 5.6704 × 10−8 W . m−2 . K−4","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"159,39,198,72\"}]"}

Question

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{"title":"Rate at which an object emits energy in the form of radiation","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,25,35,70\"}]"} {"title":"Emissivity of the object (a number between 0 and 1)","description":"Wrong","type":"incorrect","color":"#ffff00","code":"[{\"shape\":\"rect\",\"coords\":\"129,41,157,71\"}]"} {"title":"Temperature of the object on the Kelvin scale","description":"Incorrect","type":"incorrect","color":"#00ff00","code":"[{\"shape\":\"rect\",\"coords\":\"238,25,280,72\"}]"} {"title":"Surface area of the object","description":"Incorrect","type":"incorrect","color":"#ff0000","code":"[{\"shape\":\"rect\",\"coords\":\"200,28,239,72\"}]"} {"title":"Stefan-Boltzmann constant = 5.6704 × 10−8 W . m−2 . K−4","description":"Correct!","type":"correct","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"159,39,198,72\"}]"}

Review

The higher the temperature of an object of a given size, the greater the radiated power \(P\) and so the more brightly it glows.

Experiment also shows that the color of the radiation emitted by an object depends on its temperature \(T\) (Figure 26-4). A heated object emits light at all wavelengths, but emits most strongly at a particular frequency called the frequency of maximum emission. As the temperature increases, the frequency of maximum emission increases.

Equation 14-22 shows that the radiated power also depends on a quantity \(e\) called the emissivity, which depends on the properties of the object’s surface. This has its greatest value \((e = 1)\) for an idealized type of dense object called a blackbody. An ideal blackbody does not reflect any light at all, but absorbs all radiation falling on it.