Questions and answers for exam Preparation

MCQs

Heat Radiation, Thermal Properties Of Matter, Dual Nature Of Matter

Total Questions : 247 | Page 20 of 25 pages

Question 191. Four identical pieces of copper painted with different colors of paints were heated to the same temperature and then left in the environment to cool. Which of the following paint will give fast cooling?

White
Rough
Black
Shining

Discuss Question

Answer: Option C. -> Black
Answer: (c).Black

Question 192. A surface for which emissivity is constant at all temperatures and throughout the entire range of wavelength is called

Opaque
Grey
Specular
Diathermanous

Discuss Question

Answer: Option B. -> Grey
Answer: (b).Grey

Question 193. If radiant energy EB emitted by the black surface strikes the non-black surface. If non-black surface has absorptivity α, it will absorb how much radiations?

α EB
2 α EB
3 α EB
4 α EB

Discuss Question

Answer: Option A. -> α EB
Answer: (a).α EB

Question 194. A diathermanous body

Shines as a result of incident radiation
Gets heated up a result of absorption of incident radiation
Allows all the incident radiation to pass through it
Partly absorbs and partly reflects the incident radiation

Discuss Question

Answer: Option C. -> Allows all the incident radiation to pass through it
Answer: (c).Allows all the incident radiation to pass through it

Question 195. If two surfaces are at the same temperature, then the conditions correspond to mobile thermal equilibrium for which the resultant interchange of heat is zero are

3 E – α EB = 0
2 E – α EB = 0
E – α EB = 0
½ E – α EB = 0

Discuss Question

Answer: Option C. -> E – α EB = 0
Answer: (c).E – α EB = 0

Question 196. The absorptivity of black body equals to

Discuss Question

Answer: Option B. -> 1
Answer: (b).1

Question 197. Choose the false statement

Snow is nearly black to thermal radiation
Absorption of radiation occurs in a very thin layer of material n ear the surface
Transmissivity varies with wavelength of incident radiation
Most of the engineering materials have rough surfaces, and these rough surfaces give regular (specular) reflections

Discuss Question

Answer: Option D. -> Most of the engineering materials have rough surfaces, and these rough surfaces give regular (specular) reflections
Answer: (d).Most of the engineering materials have rough surfaces, and these rough surfaces give regular (specular) reflections

Question 198. A 100 W light bulb has a tungsten filament (emissivity = 0.30) which is required to operate at 2780 K. If the bulb is completely evacuated, calculate the minimum surface area of the tungsten filament