Heat Transfer

HEAT RADIATION MCQs

Total Questions : 202

Page 1 of 21 pages
Question 1. The value of transmissivity may vary from
  1.    0-1
  2.    1-2
  3.    3-4
  4.    4-5
 Discuss Question
Answer is Option A. -> 0-1
Answer: (a).0-1
Question 2. A cavity with a small hole will always behave as a
  1.    White body
  2.    Transparent body
  3.    Black body
  4.    Opaque body
 Discuss Question
Answer is Option C. -> Black body
Answer: (c).Black body
Question 3. What is the wavelength band of gamma rays?
  1.    1 * 10¯⁷ to 4 * 10¯⁴ micron meter
  2.    2 * 10¯⁷ to 2.4 * 10¯⁴ micron meter
  3.    3 * 10¯⁷ to 3.4 * 10¯⁴ micron meter
  4.    4 * 10¯⁷ to 1.4 * 10¯⁴ micron meter
 Discuss Question
Answer is Option D. -> 4 * 10¯⁷ to 1.4 * 10¯⁴ micron meter
Answer: (d).4 * 10¯⁷ to 1.4 * 10¯⁴ micron meter
Question 4. Of the radiant energy 350W/m² incident upon a surface 250W/m² is absorbed, 60W/m² is reflected and the remainder is transmitted through the surface. Workout the value for absorptivity for the surface material
  1.    0.113
  2.    0.114
  3.    0.115
  4.    0.116
 Discuss Question
Answer is Option C. -> 0.115
Answer: (c).0.115
Question 5. “Transmissivity can also be defined as ratio of transmitted radiation to that of incident energy flow”. True or false
  1.    True
  2.    False
  3.    May be
  4.    Can't say
 Discuss Question
Answer is Option B. -> False
Answer: (b).False
Question 6. The emissivity and the absorptivity of a real surface are equal for radiation with identical temperature and wavelength. This law is referred to as
  1.    Kirchhoff’s law
  2.    Lambert’s law
  3.    Planck’s law
  4.    Wein’s displacement law
 Discuss Question
Answer is Option A. -> Kirchhoff’s law
Answer: (a).Kirchhoff’s law
Question 7. The temperature of a solid surface changes from 27 K to 627 K. The emissive power changes would then confirm to the ratio
  1.    6:1
  2.    9:1
  3.    81:1
  4.    27:1
 Discuss Question
Answer is Option C. -> 81:1
Answer: (c).81:1
Question 8. Consider two bodies, one absolutely back and the other non-black and let these be at same temperature. Which one of the following statement is correct?
  1.    Black body radiates less intensively than a non-black body
  2.    Non-black body radiates less intensively than a black body
  3.    Both will radiates equally
  4.    None of them will radiates
 Discuss Question
Answer is Option B. -> Non-black body radiates less intensively than a black body
Answer: (b).Non-black body radiates less intensively than a black body
Question 9. If the temperature of a hot body is increased by 50%, the amount of radiations emitted by it would increase by nearly
  1.    200%
  2.    500%
  3.    50%
  4.    100%
 Discuss Question
Answer is Option B. -> 500%
Answer: (b).500%
Question 10. With an increase in wavelength, the monochromatic emissive power of a black body
  1.    Increases
  2.    Decreases
  3.    Decreases, reaches a minimum and then increases
  4.    Increases, reaches a maximum and then decreases
 Discuss Question
Answer is Option D. -> Increases, reaches a maximum and then decreases
Answer: (d).Increases, reaches a maximum and then decreases