MCQs of Radiation (Heat Transfer - 3151909)

Showing 21 to 27 out of 27 Questions

21.

For a perfectly black body

(a)	absorptivity $α = 1$ , reflectivity $ρ = 0$ and transmissivity $τ = 0$
(b)	$ρ = 1 a n d α = τ = 0$
(c)	$τ = 1 a n d α = ρ = 0$
(d)	$α + τ = 1 a n d ρ = 0$

22.

For an absolutely white or specular body

(a)	absorptivity $α = 1$ , reflectivity $ρ = 0$ and transmissivity $τ = 0$
(b)	$ρ = 1 a n d α = τ = 0$
(c)	$τ = 1 a n d α = ρ = 0$
(d)	$α + τ = 1 a n d ρ = 0$

23.

For a transparent or diathermanous body

(a)	absorptivity $α = 1$ , reflectivity $ρ = 0$ and transmissivity $τ = 0$
(b)	$ρ = 1 a n d α = τ = 0$
(c)	$τ = 1 a n d α = ρ = 0$
(d)	$α + τ = 1 a n d ρ = 0$

24.

The ratio of total emissive power of the body to the total emissive power of a black body at the same temperature is called

25.

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

26.

The roof of a house has been given a coating of shining metallic paint. Consequently the temperature inside the room will

(a)	fall
(b)	rise
(c)	remain unaffected
(d)	cannot be decided as it depends on factors other than the type of paint

27.

The emissivity is likely to be higher in the case of

Showing 21 to 27 out of 27 Questions