Heat Transfer Questions and Answers – Intensity of Radiations

This set of Heat Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Intensity Of Radiations”.

1. The solid angle is defined by a region by the rays of a sphere, and is measured as
a) A_n/r ²
b) A_n/r
c) A_n/r ³
d) A_n/r ⁴
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2. The plane angle is defined by a region by the rays of a circle, and is measured as
a) 3 L/ r
b) 2 L/ r
c) L/ r
d) 4 L / r
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3. When the incident surface is a sphere, the projection of surface normal to the line of propagation is the silhouette disk of the sphere which is a circle of the diameter of
a) Parabola
b) Sphere
c) Triangle
d) Hyperbola
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4. If I _n denotes the normal intensity and I _α represents the intensity at angle α, then
a) I _α = 2 I _n cos α
b) I _α = 3 I _n cos α
c) I _α = 4 I _n cos α
d) I _α = I _n cos α
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5. The intensity of normal radiation I _n is how much times the emissive power?
a) 1/π
b) 2/ π
c) 3/ π
d) 4/ π
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6. A small surface emits diffusively, and measurements indicate that the total intensity associated with emission in the normal direction I _n = 6500 W/square m sr. The emitted radiation is intercepted by three surfaces. Mark calculations for intensity associated with emission

a) 3500 W/m² sr
b) 4500 W/m² sr
c) 5500 W/m² sr
d) 6500 W/m² sr
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7. Consider a deep-space probe constructed as 1 m diameter polished aluminum sphere. Estimate the equilibrium temperature that the probe reaches if the solar energy received is 300 W/m². For solar radiation, absorptivity of aluminum is 0.3 and the average emissivity appropriate for aluminum at low temperature is 0.04
a) 415.67 K
b) 315.67 K
c) 215.67 K
d) 115.67 K
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8. The total emissive power of the emitter with area d A and temperature T is given by
a) E = 2 σ T ⁴ d A
b) E = 3 σ T ⁴ d A
c) E = σ T ⁴ d A
d) E = ½ σ T ⁴ d A
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9. A black body of 0.2 m² area has an effective temperature of 800 K. Calculate the intensity of normal radiations
a) 1234.65 W/m² sr
b) 7396.28 W/m² sr
c) 3476.74 W/m² sr
d) 8739.43 W/m² sr
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10. The energy radiated out decreases with increases in α and becomes zero at an angle of
a) 45
b) 30
c) 0
d) 90
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Sanfoundry Global Education & Learning Series – Heat Transfer.

To practice all areas of Heat Transfer, here is complete set of 1000+ Multiple Choice Questions and Answers.

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