Absorptivity MCQ

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• Electromagnetic waves strikes a hot body maintained at 900 degree Celsius which has a reflectivity of 0.66 and a transmissivity of 0.022. Let the absorbed flux be 60 W/m2. Determine the rate of incident flux
  ক

  168.67 W/m2

  খ

  178.67 W/m2

  গ

  188.67 W/m2

  ঘ

  198.67 W/m2
• Absorptivity of a body is equal to its emissivity
  ক

  Under thermal equilibrium conditions

  খ

  For a polished surface

  গ

  At one particular temperature

  ঘ

  At shorter wavelengths
• Which quantity can be neglected for gases?
  ক

  Transmissivity

  খ

  Reflectivity

  গ

  Absorptivity

  ঘ

  None can be neglected
• For a grey surface
  ক

  Reflectivity equals emissivity

  খ

  Emissivity equals transmissivity

  গ

  Absorptivity equals reflectivity

  ঘ

  Emissivity is constant
• Let 220 W/m2 of radiant energy is absorbed by a convex surface, 90 W/m2 is reflected and 40 W/m2 is transmitted through it. What is the value of absorptivity?
  ক

  0.72

  খ

  0.62

  গ

  0.52

  ঘ

  0.42
• Energy strikes a vertical hemispherical plate with an intensity of 640 W/m2. The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of absorption
  ক

  449.12 W/m2

  খ

  349.12 W/m2

  গ

  249.12 W/m2

  ঘ

  149.12 W/m2
• A body that reflects all the incident thermal radiations is called a
  ক

  Opaque body

  খ

  Gases

  গ

  Black body

  ঘ

  Specular body
• What is the absorptivity of the gray body?
  ক

  Below unity

  খ

  Unity

  গ

  2

  ঘ

  2.5
• The absorptivity of a surface depends upon (i) Direction of reflected radiation (ii) Temperature of the surface (iii) Composition Identify the correct statements
  ক

  i, ii and iii

  খ

  i and iii

  গ

  ii only

  ঘ

  ii and iii
• Energy strikes a vertical hemispherical plate with an intensity of 640 W/m2. The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of transmission
  ক

  236.74 W/m2

  খ

  116.37 W/m2

  গ

  187.87 W/m2

  ঘ

  456.09 W/m2