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# Heat Radiation Online Exam Quiz

Options

A : a. 0-1

B : b. 1-2

C : c. 3-4

D : d. 4-5

Options

A : a. 0.113

B : b. 0.114

C : c. 0.115

D : d. 0.116

Options

A : a. True

B : b. False

C : c. May be

D : d. Can't say

### A cavity with a small hole will always behave as a

Options

A : a. White body

B : b. Transparent body

C : c. Black body

D : d. Opaque body

### What is the wavelength band of gamma rays?

Options

A : a. 1 * 10¯? to 4 * 10¯? micron meter

B : b. 2 * 10¯? to 2.4 * 10¯? micron meter

C : c. 3 * 10¯? to 3.4 * 10¯? micron meter

D : d. 4 * 10¯? to 1.4 * 10¯? micron meter

### Transmissivity is defined as

Options

A : a. Fraction of total energy transmitted by the body

B : b. Fraction of total energy reflected by the body

C : c. Fraction of total energy absorbed by the body

D : d. Fraction of total energy absorbed and radiated by the body

### A polished metal pipe 5 cm outside diameter and 370 K temperature at the outer surface is exposed to ambient conditions at 295 K temperature. The emissivity of the surface is 0.2 and the convection coefficient of heat transfer is 11.35 W/m² degree. Calculate the overall coefficient of heat transfer by the combined mode of convection and radiation

Options

A : a. 11.04 W/m² degree

B : b. 12.04 W/m² degree

C : c. 13.04 W/m² degree

D : d. 14.04 W/m² degree

### Radiant energy with an intensity of 800 W/m² strikes a flat plate normally. The absorptivity is thrice the reflectivity and twice the transmissivity. Determine the rate of transmission

Options

A : a. 155.47 W/m²

B : b. 145.47 W/m²

C : c. 135.47 W/m²

D : d. 125.47 W/m²

### With respect to incident radiation, transmissivity varies with

Options

A : a. Time

B : b. Temperature

C : c. Surface area

D : d. Wavelength

### A body through which all the incident radiations passes, is called

Options

A : a. Opaque body

B : b. Black body

C : c. Transparent body

D : d. White body

### Reflectivity is defined as

Options

A : a. Fraction of total energy transmitted by the body

B : b. Fraction of energy reflected by the body

C : c. Fraction of total energy absorbed by the body

D : d. Fraction of total energy absorbed and radiated by the body

Options

A : a. 0.8 W

B : b. 0.3 W

C : c. 0.9 W

D : d. 0.10 W

Options

A : a. 1 and 2

B : b. 2 and 3

C : c. 2 only

D : d. 1 and 3

### When a surface absorbs a certain fixed percentage of striking radiation the surface is called

Options

A : a. Grey body

B : b. Black body

C : c. White body

D : d. Opaque body

### Which one is true regarding gases?

Options

A : a. Reflectivity is unity

B : b. Absorptivity is zero

C : c. Reflectivity is zero

D : d. Transmissivity is zero

### Thin glass plate is an example of

Options

A : a. Transparent body

B : b. Opaque body

C : c. Black body

D : d. White body

### Which one is true for opaque body?

Options

A : a. Transmissivity is zero

B : b. Reflectivity is zero

C : c. Absorptivity is zero

D : d. Reflectivity is unity

### Energy strikes a vertical hemispherical plate with an intensity of 640 W/m². The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of transmission

Options

A : a. 236.74 W/m²

B : b. 116.37 W/m²

C : c. 187.87 W/m²

D : d. 456.09 W/m²

### The absorptivity of a surface depends upon (i) Direction of reflected radiation (ii) Temperature of the surface (iii) Composition Identify the correct statements

Options

A : a. 1, 2 and 3

B : b. 1 and 3

C : c. 2 only

D : d. 2 and 3

### What is the absorptivity of gray body?

Options

A : a. Below unity

B : b. Unity

C : c. 2

D : d. 2.5