CameraIcon

SearchIcon

MyQuestionIcon

1

You visited us 1 times! Enjoying our articles? Unlock Full Access!

Emissive and Absorptive Power

The thermal r...

Question

The thermal radiation emitted by a body is proportional to Tⁿ where T is its absolute temperature. The value of n is exactly 4 for

(a) a blackbody
(b) all bodies
(c) bodies painted black only
(d) polished bodies only

Open in App

Solution

(b) all bodies

From Stefan-Boltzmann law, the energy of the thermal radiation emitted per unit time by a blackbody of surface area A is given by
$u = σ A T^{4}$
Here, $σ$ is Stefan-Boltzmann constant.
This law holds true for all the bodies.

Suggest Corrections

thumbs-up

0

Similar questions

Q. The thermal radiation emitted by a body is proportional to

T^{n}

T

is its absolute temperature. The value of

n

4

Q. All bodies emit heat energy from their surfaces by virtue of their temperature. This heat energy is called radiant energy of thermal radiation. The heat that we receive from the sun is transferred to us by a process which, unlike conduction or convection, does not require the help of a medium in the intervening space which is almost free of particles. Radiant energy travels in space as electromagnetic spectrum. Thermal radiations travel through vacuum with the speed of light. Thermal radiations obey the same laws of reflection and refraction as light does. They exhibit the phenomena of interference, diffraction and polarization as light does.
The emission of radiation from a hot body is expressed in terms of that emitted from a reference body (called the black body) at the same temperature. A black body absorbs and hence emits radiations of all wavelengths. The total energy E emitted by a unit area of a black body per second is given by

E = σ T^{4}

where T is the absolute temperature of the body and

σ

is a constant known as Stefan's constant. If the body is not a perfect black body, then

E = ε σ T^{4}

ε

is the emissivity of the body.
When a body A at a higher temperature

T_{1}

is surrounded by another body B at a lower temperature

T_{2}

, then the rate of loss of heat from body A will be proportional to :

Q. The rate at which a black body emits radiation at a temperature

T

is proportional to:

Q. All bodies emit heat energy from their surfaces by virtue of their temperature. This heat energy is called radiant energy of thermal radiation. The heat that we receive from the sun is transferred to us by a process which, unlike conduction or convection, does not require the help of a medium in the intervening space which is almost free of particles. Radiant energy travels in space as electromagnetic spectrum. Thermal radiations travel through vacuum with the speed of light. Thermal radiations obey the same laws of reflection and refraction as light does. They exhibit the phenomena of interference, diffraction and polarisation as light does.
The emission of radiation from a hot body is expressed in terms of that emitted from a reference body (called the black body) at the same temperature. A black body absorbs and hence emits radiations of all wavelengths. The total energy

E

emitted by a unit area of a black body per second is given by

E = σ T^{4}

T

is the absolute temperature of the body and

σ

is a constant known as Stefan's constant. If the body is not a perfect black body, then

E = ε σ T^{4}

ε

is the emissivity of the body.
In which region of the electromagnetic spectrum do thermal radiations lie?

Q. Intensity of heat radiation emitted by body is believed to be proportional to fourth power of absolute temperature of the body. The proportionality constant also known as Boltzmann's constant may have possible value of :

View More

Join BYJU'S Learning Program

similar_icon

Related Videos

lock

Laws of Radiation

PHYSICS

Watch in App

explore_more_icon

Explore more

Emissive and Absorptive Power

Standard XII Physics

Join BYJU'S Learning Program

CrossIcon