All radiations in a black body are___________________?

Related Mcqs:

1. Emissivity of a white polished body in comparison to a black body is________________?

   A. higher
   B. lower
   C. same
   D. depends upon the shape of body
   E. none of the above

2. Total emissivity of polished silver compared to black body is___________________?

   A. same
   B. higher
   C. more or less same
   D. very much lower
   E. very much higher

3. A perfect black body is one which_______________?

   A. is black in colour
   B. reflects all heat
   C. transmits all heat radiations
   D. abslprbs heat radiations of all wave lengths falling on it
   E. fully opaque

4. 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
   E. area and time

5. 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
   E. l/T

6. 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
   E. a = 0,x + p= 1.
   where a = absorptivity, p == reflectivity, X = transmissivity

7. 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
   E. Black body law

8. When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by __________________?

   A. conduction
   B. convection
   C. radiation
   D. conduction and convection
   E. convection and radiation

9. 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
   E. 0.60

10. 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
    E. a=0,x + p= 1.

    where a = absorptivity, p = reflectivity, X = transmissivity