Tag: energy production

Questions Related to energy production

Black body spectrum is

physics energy production perfectly black body black-body radiation black body radiation

  1. continuous absorption

  2. line absorption

  3. continuous emission

  4. line emission

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Correct Option: C
Explanation:

Black Body radiation involves emission of a number of wavelengths, which by definition is continuous emission.

Stefan-Boltzmanns Law for a perfect black body is represented by

physics energy production perfectly black body black-body radiation black body radiation

  1. $\dfrac{dQ}{dt} = \sigma AT^2 $

  2. $\dfrac{dQ}{dt} = \sigma AT^3 $

  3. $\dfrac{dQ}{dt} = \sigma AT^4 $

  4. $ Q = \sigma AT^4 $

Show answer
Correct Option: C
Explanation:
Stefan boltzmann's law, $\Rightarrow \cfrac { dQ }{ dt } =\sigma A\varepsilon { T }^{ 4 }$
( for black body, $\varepsilon=1$)
So, for black body stefan's boltzmann's law is $\Rightarrow \cfrac { dQ }{ dt } =\sigma A { T }^{ 4 }$
Stefan's boltzmann's law states that total energy radiated from a surface is proportional to the forth power of its absolute temperature.

Ferry's black body is accurately represented by 

physics energy production perfectly black body black-body radiation black body radiation

  1. A fine hole in a double walled spherical cavity.

  2. A fine hole in a double walled spherical cavity, evacuated and painted black.

  3. A fine hole in a spherical cavity, evacuated and painted black.

  4. A fine hole in a black cavity.

Show answer
Correct Option: B
Explanation:

Ferry's black body is accurately represented by a fine hole in a double walled spherical cavity, evacuated and painted black.

$\rightarrow$ Ferry designed the simplest black body. It is a double walled evacuated spherical cavity whose inner wall is blackened. The space between wall is evacuated to prevent heat loss by conduction and radiation. There is a fine hole in it. All the radiations incident upon this hole are absorbed by this black body. 

Ferry's black body is 

physics energy production perfectly black body black-body radiation black body radiation

  1. a perfect reflector of heat.

  2. perfectly black.

  3. platinum black.

  4. almost perfectly black.

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Correct Option: D
Explanation:
Ferry's black body is almost perfectly black.
As because emission of heat and absroption of heat takes place completely.

Black body radiation is

physics energy production perfectly black body black-body radiation black body radiation

  1. White

  2. IR

  3. Black

  4. UV

Show answer
Correct Option: A
Explanation:

a black body looks black because it absorbs light of all colors. so when it radiates energy as light, it will release all the colors which it had absorbed resulting in the emission of white light, because white light is the resultant of many component colors.

The original temperature of a black body is $727^\circ C$. Calculate temperature at which total radiant energy from this black body becomes double:

physics energy production perfectly black body black-body radiation black body radiation

  1. $971K$

  2. $1189K$

  3. $2001K$

  4. $1458K$

Show answer
Correct Option: B
Explanation:

$Rediant Energy = \sigma T^2$

$Energy = \sigma (1000)^4$
$E _2 = 2 E _1$
$Then$
$\sigma T _2 ^{4} = 2 \times \sigma (1000)^4$
$T _2 = 2^\frac{1}{4} \times1000$
$T _2 = 1189 K$

Temp. of black body is $3000K$ when black body cools. Then change in wavelength $\Delta \lambda=9$ micron corresponding to maximum energy density. Now temp. of black body is:

physics energy production perfectly black body black-body radiation black body radiation

  1. $300K$

  2. $2700K$

  3. $270K$

  4. $1800K$

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Correct Option: A

The rate of emission of radiation of a black body at 273$^{ \circ  }{ C }$ is E, then the rate of emission of radiation  of this body at 0$^{ \circ  }{ C }$ will be :-

physics energy production perfectly black body black-body radiation black body radiation

  1. $\dfrac { E }{ 16 } $

  2. $\dfrac { E }{ 4 } $

  3. $\dfrac { E }{ 8 } $

  4. 0

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Correct Option: A

For non black bodies, the range of values of emissivity $e$ is 

physics energy production perfectly black body black-body radiation black body radiation

  1. $- 1 < e < 1 $

  2. $- 1 < e < 0 $

  3. $ 1 < e < 2 $

  4. $0 < e < 1 $

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Correct Option: D

A blackbody does not

physics energy production perfectly black body black-body radiation black body radiation

  1. emit radiation

  2. absorb radiation

  3. reflect radiation

  4. refract radiation

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Correct Option: B