Railways Technical Ability Vibration Analysis Question Bank Vibration Analysis

  • question_answer For an opaque plane surface, the irradiation, radiosity and emissive power are respectively 20, 12 and \[10\,\,\text{W/}{{\text{m}}^{\text{2}}}.\] what is the emissivity of the surface?

    A) 0.2                               

    B) 0.4

    C) 0.8                               

    D) 1.0

    Correct Answer: C

    Solution :

    Radiosity, \[J=\varepsilon {{E}_{b}}+(1-\varepsilon )G\] Where G = Irradiation \[=20\,\,\text{W/}{{\text{m}}^{\text{2}}}\] \[{{E}_{b}}=\] emissive power \[=10\,\,\text{W/}{{\text{m}}^{\text{2}}}\] \[I=12\,\,\text{W/}{{\text{m}}^{\text{2}}}\] \[12=\varepsilon \times 10+(1-\varepsilon )\times 20\] \[\varepsilon =0.8\]

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