A grey body is one whose absorptivity _________________?
(A) varies with temperature
(B) varies with the wave length of incident ray
(C) varies with both
(D) does not vary with temperature and wave length of the incident ray
(D) there is no such criterion
According to Wien’s law, the wavelength corresponding to maximum energy is proportion to ________________?
(A) absolute temperature (T)
(B) I2
(C) f
(D) t
(D) 1/r
Depending on the radiating properties, a body will be opaque when _________________?
(A) p = 0, x = 0 and a = 1
(B) p=l,x = 0anda = 0
(C) p = 0, x = 1 and a = 0
(D) x – 0, a + p = 1
(D) a=0,x + p= 1.
Depending on the radiating properties, a body will be white when_________________?
(A) p = 0, x = 0 and a = 1
(B) p=l,T = 0anda = 0
(C) p = 0, x = 1 and a = 0
(D) x = 0, a + p = 1
(D) a = 0, x + p = 1.
The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as_________________?
(A) Krichoff’s law
(B) Stefan’s law
(C) Wien’ law
(D) Planck’s law
(D) Black body law
The thermal diffusivities for solids are generally__________________?
(A) less than those for gases
(B) jess than those for liquids
(C) more than those for liquids and gases
(D) more or less same as for liquids and gases
(D) zerci
According to Stefan’s law, the total radiation from a black body per second per unit area is proportional to____________________?
(A) absolute temperature
(B) T2
(C) T5
(D) t
(D) l/T
Depending on the radiating properties, a body will be black when_________________?
(A) p = 0, x = 0 and a = 1
(B) p= l,T = 0anda = 0
(C) p = 0, x = 1 and a = 0
(D) x = 0, a + p = 0
(D) a = 0,x + p= 1. where a = absorptivity, p == reflectivity, X = transmissivity
The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit_______________?
(A) temperature
(B) thickness
(C) area
(D) time
(D) area and time
40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is____________________?
(A) 0.45
(B) 0.55
(C) 0.40
(D) 0.75
(D) 0.60