RADIATION BASICS MULTIPLE CHOICE QUESTIONS (MCQ) WITH ANSWERS

RADIATION BASICS MULTIPLE CHOICE

QUESTIONS (MCQ) WITH ANSWERS 

 

MCQ on radiation basics help to

understand it deeply. It increases level of

clarity. It help in the design of  radiating

surfaces with higher efficiency and less

cost.

Fig. Black Body- Spherical body ( A radiation from
a point ‘O’  to ABCDE is entrapped due to multi-reflections)

Fig. Absorption, Reflection and Transmission of Radiations
incident on a grey body

Fig. Wien’s Displacement Law

Fig. Spectrum Electromagnetic Radiations
  1. Radiation is energy transmission between source and receiver without any

  1. Chemical contact

  2. Physical contact

  3. Chemical & physical contact

  4. None

ANS: (b)

  1. Do radiations affect the material medium in between the source and the receiver

  1. Yes

  2. No

  3. Yes & no

  4. None

ANS: (b)

  1. Best radiation exchange takes place in

  1. Air

  2. Water

  3. Vacuum

  4. None

ANS: ©

  1. A material medium present between the source and the receiver

  1. Reduce the radiations

  2. Increase the radiations

  3. Decrease & increase the radiations

  4. None

ANS: (a)

  1. Energy released by a radiating surface is

  1. Intermittent

  2. Continuous

  3. Intermittent & continuous

  4. None

ANS: (a)

  1. Radiations are in the form of

  1. Electric waves

  2. Magnetic waves

  3. Electro-magnetic waves

  4. None

ANS: (c )

  1.  The source of Electro-magnetic radiations is 

  1. Vibrational movements of sub-atomic particles

  2. Rotational movements of sub-atomic particles

  3. (a) & (b)

  4. None

ANS: (c )

  1. Thermal radiations depend upon

  1. Nature of the emitting surface

  2. Temperature of the emitting surface

  3. Nature & temperature of the emitting surface

  4. None

ANS: (c )

  1. The distinction between various types of radiation  depends upon

  1. Frequency

  2. Wavelength

  3. Frequency & wavelength

  4. None

ANS: (c )

  1. Higher energy radiations have

  1. High frequency & high wavelength

  2. High frequency and lower wavelength

  3. Low frequency & low wavelength

  4. None

ANS: (b)

  1. The product of wavelength and frequency is the velocity of

  1. Sound

  2. Light

  3. Sound & light

  4. None

ANS: (b)

  1. A radiating surface at high temperature has

  1. High frequency

  2. Higher wavelength

  3. Higher frequency & higher wavelength

  4. None

ANS: (a)

  1. Units of Wavelength of a radiation is 

  1. mm

  2. m

  3. µm

  4. None

ANS: (c )

  1. One micron (1 µm) is equal to

  1.   Firstly           10-4 m

  2.   Secondly      10-6 m

  3.    Thirdly         10-8 m

  4. None

ANS: (b)

  1. Planck’s constant used in radiation analysis is

  1. Firstly       625 x 10-34 J/s

  2. Secondly  625 x 10-34 J/s

  3.   Thirdly    625 x 10-34 J/s

  4. None

ANS: (b)

  1. A solid body emits a

  1. Continuous spectrum

  2. Selective spectrum

  3. Continuous & selective spectrums

  4. None

ANS: (a)

  1. Liquid body emits a

  1. Continuous spectrum

  2. Selective spectrum

  3. Continuous & selective spectrums

  4. None

ANS: (a)

  1. A gas and a vapor body emits a

  1. Continuous spectrum

  2. Selective spectrum

  3. Continuous & selective spectrums

  4. None

ANS: (b)

  1. The range of wavelength of thermal radiations is

  1. 1 to 10 µm

  2. 0.1 to 100 µm

  3. 1 to 100 µm

  4. None

ANS: (c )

  1. The wavelength range of solar radiation is

  1. 1 to 10 µm

  2. 0.1 to 100 µm

  3. 1 to 4 µm

  4. None

ANS: (c )

  1. Thermal radiations consists of

  • Infrared radiations

  • Visible & partly ultra-violet radiations

  • (A) & (b)

  • None

ANS: (c )

  1. Thermal radiations follow

  1. Magnetic laws

  2. Optical laws

  3. Magnetic & optical laws

  4. None

ANS: (b0

  1. Radiations given by a body depends upon

  1.  Temperature difference gradient

  2.  Difference of Temperature 

  3.  Temperature of the body

  4. None

ANS: (c )

  1. Thermal radiations are

  1. Reflected & transmitted

  2. Transmitted & absorbed

  3. Reflected, transmitted & absorbed

  4. None

ANS: (c )

  1. Rate of heat transfer is same for conduction for temperatures combinations of 1200 & 2000C and 1800 &8000 . Radiation exchange in two cases is

  1. Constant

  2. Different

  3. Constant & different

  4. None

ANS: (b)

  1. The body emits radiations in a certain spectrum and

  1. Reflect radiations in the same spectrum

  2. Transmit radiations in the same spectrum

  3. Absorb radiations in the same spectrum

  4. None

ANS: (c )

     27. Plank’s law gives the radiation flux for a

(a) A single wavelength

(b)  Two wavelengths

( c) Three wavelengths

(d) None

ANS: (a)

     28. Plank’s law gives the radiation flux for a

(a) A Black body

(b)  A Grey body

( c) All types of bodies

(d) None

ANS: (a)

     29. Stefan’s Boltzmann law is for a

(a) A single wavelength

(b)  Two wavelengths

( c) Three wavelengths

(d) None

ANS: (d)

     30. Stefan’s Boltzmann law is for a

(a) A Black body

(b)  A Grey body

( c) All types of bodies

(d) None

ANS: (a)

        31. Planck’s law for spectral distribution of emissive power for a black body

  1. Firstly    (Eλ)b =C1 λ-5/(eC2/λT) -1

  2. Secondly    (Eλ)b =C1 λ-5/(eC2/λT -1)

  3. Thirdly    (Eλ)b =C1 λ-5/(eC2/λT +1)

  4. None

ANS: (a)

      32. Spectral distribution of thermal radiation means

  1. Firstly  Variation with respect to wavelength

  2. Secondly  Variation with respect to frequency

  3. Thirdly  Variation with respect to wavelength & frequency

  4. None

ANS: (a)

       33. Spatial radiation distribution means

  1. Firstly  Variation of radiation in a line

  2. Secondly  Variation of radiation in a plane

  3. Thirdly  Variation of radiation in space

  4. None

ANS: (c )

    34. Value of constant C1 in Planck’s equation is

  1. 4385 x 10-2 mK

  2. 374 x 10-15 Jm2/s

  3. 67 x 10-8 W/m2 K4

  4. None

ANS: (b)

    35. Value of constant C2 in Planck’s equation is

  1. 4385 x 10-2 mK

  2. 374 x 10-15 Jm2/s

  3. 67 x 10-8 W/m2 K4

  4. None

ANS: (a)

    36. Modified Planck’s law for shorter wavelengths is

  1. Firstly         (Eλ)b =C1 λ-5/(eC2/λT)

  2. Secondly    (Eλ)b =C1 T/C2λ4

  3. Thirdly      (Eλ)b =C1 λ-5/(eC2/λT-1)

  4. None

ANS: (a)

    37. Modified Planck’s law for large wavelengths is

  1. Firstly      (Eλ)b =C1 λ-5/(eC2/λT)

  2. Secondly   (Eλ)b =C1 T/C2λ4

  3. Thirdly       (Eλ)b =C1 λ-5/(eC2/λT-1)

  4. None

ANS: (a)

    38. Rayleigh’s law of radiation for a black body is

  1. Firstly       (Eλ)b =C1 λ-5/(eC2/λT)

  2. Secondly   (Eλ)b =C1 T/C2λ4

  3. Thirdly       (Eλ)b =C1 λ-5/(eC2/λT-1)

  4. None

ANS: (b)

    39. Rayleigh’s law of radiation for a black body is applicable for value of λT is

  1. >5 x 105 µK

  2. >7 x 105 µK

  3. > 8 x 105 µK

  4. None

ANS: (c )

    40. Rayleigh’s law of radiation is applicable to thermal radiations

  1. No

  2. Yes

  3. Can’t say

  4. None

ANS: (a)

    41. The monochromatic emissive power increases with the

  1. Increase of temperature

  2. Decrease of temperature

  3. Increase & decrease of temperature

  4. None

ANS: (a)

    42. The monochromatic emissive power varies with

  1. Increase of wavelength

  2. Decrease of wavelength

  3. Increases with increase of wavelength & then decreases with the increase of wavelength

  4. None

ANS: (c )

    43. At a particular wavelength, the monochromatic emissive power increases increases with the

  1. Increase of temperature

  2. Decrease of temperature

  3. Increase & decrease of temperature

  4. None 

    44. As temperature increases, the wavelength at which emissive power is maximum shifts towards

  1. Larger wavelength

  2. Shorter wavelength

  3. Both larger & shorter wavelengths

  4. None

ANS: (b)

    45. At any temperature, the area under

 the curve of monochromatic emissive power vs wavelength is within the wavelength as

  1. Firstly     λ12

  2. Secondly     λ1–λ2

  3. Thirdly      λ1 + λ2

  4. None

ANS: (b)

    46. Stefan-Boltzman law gives for a black body

  1. Monochromatic emissive

  2. Total emissive power

  3. (Monochromatic + total) emissive power

  4. None

ANS: (b)

    47. Stefan-Boltzman law equation for a black body is

  1. σb A T4

  2. σb T4

  3. € σb T4

  4. None

ANS: (b)

    48. Temperature T used in Stefan-Boltzman equation is in

  1. 0C

  2. 0F

  3. K

  4. None

ANS: (c )

    49. The value of Stefan-Boltzman constant σb is

  1. 77 x 10-8 W/m2K4

  2. 67 x 10-8 W/m2K4

  3. 57 x 10-8 W/m2K4

  4. None

ANS: (b)

    50. Wien’s Displacement Law equation is

  1. Firstly        λ T= Constant

  2. Secondly    λm T = Constant

  3. Thirdly        λ2 T = Constant

  4. None

ANS: (b)

    51. The value of the product of absolute temperature and the wavelength at which emissive power is maximum is

  1. 285 x 105 T5 W/m2

  2. 9 x 10-3 µm K

  3. 9 x 10-3 µm K

  4. None

ANS: (b)

    52. Emissivity of a body is

(a) Firstly Equal to the reflectivity

(b) Secondly Equal to the transmissivity

(c) Thirdly Equal to the absorptivity

(d) None

ANS: ©

    53. Emissivity of a body is

    • (a) Equal to the reflectivity

    • (b) Less than the reflectivity

    • (c) More than the reflectivity

    • (d) None

ANS: (d)

    54. Emissivity of a grey body is

    • (a) Equal to the absorptivity

    • (b) Less than the absorptivity

    • (c) More than the absorptivity

    • (d) None

ANS: (a)

    55. Emissivity of a real body is

    • (a) Equal to the transmissivity

    • (b) Less than the transmissivity

    • (c) More than the transmissivity

    • (d) None

ANS: (d)

    56. Kirchhoff’s law states that the ratio of

    • (a) Reflectivity to absorptivity is constant

    • (b) Absorptivity to transmissivity is constant

    • (c) Transmissivity and absorptivity is constant

    • (d) None

ANS: (d)

    57. Kirchhoff’s law states that at a certain temperature the ratio of

    • (a) Emissive power of a grey and black body is constant

    • (b) Emissive power of a black and grey body is constant

    • (c) Emissive power of all grey bodies is constant

    • (d) None

ANS: (a)

    58. Wien’s Displacement law deals with emissive power of a body of

    • (a) All wavelengths

    • (b) Single wavelength

    • (c) Two wavelengths

    • (d) None

ANS: (b)

    59. Wien’s Displacement law deals with peak emissive power of a body at

    • (a) All temperatures

    • (b) Single temperature

    • (c) Average of all temperatures

    • (d) None

ANS: (b)

    60. As per Wien’s Displacement law, the product of peak wavelength and

    • (a) Emissivity is constant

    • (b) Reflectivity is constant

    • (c) Temperature is constant

    • (d) None

ANS: ©

61. Semi transparent bodies radiate energy

    • (a) In a hemi spherical space

    • (b) In a cylindrical shape

    • (c) In a spherical shape

    • (d) None

ANS: (c)

    62. Non-transparent bodies radiate energy in a

    • (a) In a hemi spherical space

    • (b) In a cylindrical shape

    • (c) In a spherical shape

    • (d) None

ANS: (a)

    63. The total energy emitted by a real body, regardless of the wavelengths, is given by

    • (a) E =σ A T4

    • (b) E =εσ A T4

    • (c) E =ε A T4

    • (d) None

ANS: (d)

    64. The total energy emitted by a real body, regardless of the wavelengths, is given by

    • (a) E =σ A T4

    • (b) E =εσ A T4

    • (c) Q. =ε A T4

    • (d) None

ANS: (c)

    65. As per Lambert’s Cosine law

    • (a) Iϴ = In sin ϴ

    • (b) Iϴ = In cos ϴ

    • (c) Iϴ = In tan ϴ

    • (d) None

ANS: (b)

    66. As per Lambert’s Cosine law

    • (a) In = Iϴ sin ϴ

    • (b) In = Iϴ cos ϴ

    • (c) In= Iϴ tan ϴ

    • (d) None

ANS: (d)

    67. Radiation emissive power  density is equal to the

    • (a) Eb

    • (b) Eb x π

    • (c) Eb

    • (d) None

ANS: ©

    68. Law for the monochromatic radiation emissive power is

(a) Stephen’s Boltzmann Law

(b) Planck’s Law

(c) Wien’s displacement Law

(d)None

ANS: (b)

    69. Radiosity is defined as

  • (a) Total reflected radiations

  • (b) Total emitted radiations

  • (c) Difference of emitted and reflected radiations

  • (d) None

  • ANS: (b)

    70. Absorptivity is zero for an opaque

  • (a) Black body

  • (b) White Body

  • (c) Grey body

  • (d) None

  • ANS: (b)

    71. As per Kirchhoff’s law

  • (a) Radiosity = absorptivity

  • (b) Reflectivity = absorptivity

  • (c) Emissivity= absorptivity

  • (d) None

  • ANS: (c)

    72. Radiation is most prominent in

  • (a) Fluids

  • (b)Solids

  • (a) Gases

  • (d) None

  • (Ans: d)

     73. Which Law gives the monochromatic emissive power?

(a) Stefan’s Boltzmann Law

(b) Kirchhoff’s Law

(c) Wien’s Displacement Law

(d) None

ANS: (d)

    74. All types of radiations are emitted from a body at

(a) Room temperature

(b) Boiling temperature of water

(c) Melting temperature of steel

(d) None

ANS: (d)

     75. Radiations are more harmful with

(a) Large wavelengths

(b) Short wavelengths

(c) Large as well as short wavelengths

(d) None

ANS: (b)  

    76. The wavelength at the peak value of monochromatic emissive power

(a) Increases with the increase of temperature

(b) Decreases with the decrease of temperature

(c) Increases with the decrease of temperature

(d) None

ANS: (c)

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