Introduction
Josef Stefan and Ludwig Boltzmann together proposed the law of black body radiation. According to the law, the total heat radiation emitting from a black body is directly proportional to the fourth power of the thermodynamic or absolute temperature of the black body. The proportionality constant used for this equation was named Stefan Boltzmann constant and was expressed by the Greek symbol σ.
Value of Stefan Boltzmann Constant
Stefan’s constant was universally accepted, and its value was derived as
σ = 5.670367(13) × 10-8 W ⋅ m-2. K-4
From the above, the SI unit of Stefan’s constant can be written as W ⋅ m-2. K-4.
Here,
W stands for Watt.
m for Metre.
K for Kelvin.
Dimensional formula for Stefan Boltzmann law constant will be \[[M^1T^{-3}K^{-4}]\].
Beside the SI unit, Stefan Boltzmann Constant can be expressed in various other systems of the unit as well. Here, look at the table below for the same.
Formula for Stefan Boltzmann Constant Value
This value is derived using various other constants or evaluated experimentally as shown below:
σ = 2 . π5 KB4 / 15 h3 c2 = 5.670367(13) × 10-8 J . m-2. S-1 . K-4
Refer to the table mentioned below to know the physical quantities used in this equation.
According to CODATA, this Value of Stefan constant can be evaluated utilising this gas constant as mentioned below.
σ = 2π5 R4 / 15 h3 c2 NA4 = (32 π5 h R4 R∞4) / (15 Ar(e)4 Mu4 c6 α8)
Refer to the table mentioned below to know the physical quantities used in this equation and their values.
You need to give special attention to these tables as these are something that have more to do understanding before learning. You need to keep in mind that this part cannot be mugged up in any way. Therefore, your focus should be on gaining clarity of basic concepts. For this, Vedantu tutors hold your hand from initial to the end where you can attain clarity on simple to complex topics. Once you have gained knowledge on concepts, then you can move ahead towards uses and applications.
Stefan Boltzmann constant – Uses and Applications
There are several scenarios in Physics when this constant is used for determining various physical quantities and other constants. Here is a list of few applications –
This constant can be used for measuring the heat amount which a black body radiates.
This constant is handy for the conversion of units (Temperature K into intensity (W. m-2).
These are a few applications of Stefan constant value amongst several others. Knowing the value of this constant and how it is derived will help you in the calculation of several other physical quantities. Going further, answer the questions mentioned below and test your understanding of this topic.
Multiple Choice Questions
1.Choose the appropriate option which holds true for Stefan Boltzmann thermal radiation law.
q = α A T5
q = α A T
q = α A T3
q = α A T4
Ans: d
2.Choose the appropriate unit for Stefan Boltzmann’s constant.
Kcal/hr K4
Kcal/m2 hr K4
Kcal/m2 K4
Kcal/m hr K4
Ans: b
You will be able to extend your learning about the Stefan's constant and more with Vedantu’s study materials. Now you can also download our Vedantu app and easily learn the complex topics with the study notes prepared by our expert tutors.
1.What is the unit of Stefan’s constant?
Ans: The SI Unit of Stefan’s constant can be written as W ⋅ m-2. K-4. In CGS units, it can be expressed as erg.cm2.s1.K4, and in US customary units, it is BTU.hr1.ft2.°R4.
To support the preparation of students, Vedantu has also included a few MCQs that give an idea of the types of multiple types questions that could be there in the final examination. For regular practice, join Vedantu classes using the web portal or mobile applications.
FAQs on Stefan Boltzmann Constant
1.What is the unit of Stefan’s constant?
SI Unit of Stefan’s constant can be written as W ⋅ m-2. K-4. In CGS units, it can be expressed as erg.cm2.s1.K4, and in US customary units, it is BTU.hr1.ft2.°R4. So, if you are a student of Physics, then you must be aware of the unit of Stefan Constant and for a detailed study, you can have the guidance of expert tutors from an educational portal like Vedantu. With good study material, you can expect to raise your score along with your knowledge.
2.What is the black body?
A black body is considered as an ideal physical body that is capable of absorbing all electromagnetic radiation incidents on it, irrespective of the angle of incidence or its frequency. In Physics, it is spelt in two ways the first is the black body and the second one is a blackbody. This is known as a surface that is responsible for absorbing all the radiant energy that falls over it. The term comes to light as this visible light gets absorbed in place of the reflection. Therefore, the surface also turns black.
3.What is Stefan’s law of black body radiation?
According to Stefan’s law of black body radiation, all the radiation emitting from a black body is proportional to the fourth power of the absolute or thermodynamic temperature of the black body. The Stefan–Boltzmann law is also called Stefan Constant Law that the whole energy starts radiating as per the surface unit area within a black body as per a unit frame. You can know it in varied ways as the black body, radiant flux, energy-flux density, or it can be emissive power, j*. It is proportional to a black body's fourth power.
4.Why is Vedantu good to go for Stefan Boltzmann Constant law?
Vedantu has emerged rapidly for studying at the comfort of home. If you are looking for a good platform to understand the Stefan Boltzmann Constant law, then Vedantu is an ideal platform as the tutors here have described the law according to definitions, formulas, values, uses and application in a detailed manner. The language has been kept really simple where students do not have to keep the dictionary by their side every time. Plus, the Vedantu is present to serve you around the clock.
5.What is the best method to learn formulas for Stefan Boltzmann Constant law in an easy manner?
If you are eager to learn the formulas based on Stefan Boltzmann Constant law in an uncomplicated manner then Vedantu guides the students to keep daily practice as their routine. They should ensure that whatever they learn each day, they should revise it multiple times so that all the formulas come to their fingertips. Next to this, the students have to remember that shortcuts are not available to learn any chapter or its formulas. Thus, they must maintain a regular routine to do something out of the box.
