Wien displacement law 
                     Wien  
displacement 
lJayamw chemistry adda 
 presents
02
Wilhelm Wein, in 
1893,  derived a 
formula to  measure 
the highest  spectral 
radiance of a  
blackbody as a 
function  of its 
wavelength at a  
particular temperature  
and is renowned as 
Wien  displacement 
law.
Overvie
It unfolded thew shift of peak-intense 
wavelength towards  shorter wavelengths at 
higher temperatures. Hence, the  term 
'displacement" implies the movement of crest  
wavelength to shorter wavelengths.
Moreover, the Wien displacement law interprets 
an  inversely proportional relationship of 
maximum intense  blackbody radiation 
wavelength (λm) with its absolute  temperature. 
And the law held good at shorter wavelengths  
of radiation emissions but failed to give 
accurate results at  longer wavelengths.
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The Wien displacement law formula is a 
 temperature-specific empirical relation 
for the  peak-intense wavelength of a 
blackbody curve.
λm x T = 
Wien  b
Where,
displacemen λm denotes the wavelength of thermal 
t  law radiation  with peak intensity.
T= absolute temperature of the body.
formula b=Wien's constant. The numerical 
value of Wien's  proportionality constant 
is 2.89 x 10 -̂3 meter  Kelvin, and the 
alphabet 'b' symbolizes it.
Wien displacement 
 law and 
wWitah vthee linevnengtiotnh of the mathematical 
formula,  Wien concluded that the 
product of the zenith  wavelength with 
the body's temperature is always  
constant in thermal equilibrium 
conditions.
It's possible to quantify the temperature 
of an object  from the radiation 
wavelength by Wien's law and  vice versa.
At room temperature, for 25 degrees 
centigrade, the  highest wavelength of 
intense radiation is 9.6  micrometers.
Similarly, for 30 degrees centigrade, the highest wavelength of intense 
radiation is 9.3  micrometers.
Both these examples show that, at room temperature conditions, hot objects 
emit energies in the  infrared region predominantly.
When the radiation color is yellow with 550 nm wavelength, its temperature 
will be 5255 Kelvin,  following Wien's formula.
Likewise, if the radiation temperature is 7225 Kelvin, it is white-colored with 
400 nm wavelength.
It contradicts our assumption that red objects are hot and white bodies are 
cold. White-colored  materials possess the highest temperature of all the other 
colors of visible radiations.
Finally, the Wien displacement law graph for the peak wavelength positions of 
hot material at its  absolute temperatures shows a Blilonge: arly declining curve.
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The product of λm with the body's 
temperature  on the Kelvin scale is a 
fixed number called the  Wien 
displacement law constant.
λm x T = 
Wien  b
It defines the inversely varying relationship 
displacemen of  maximum intense hot electromagnetic 
t  law radiation  wavelength with the object's 
temperature in thermal  equilibrium 
constant conditions.
The numerical value of Wien's 
proportionality  constant is 2.89 x 
10^-3 mK, and the alphabet 'b'  
symbolizes it.
Wien displacement 
law  applications
What does it Where is it used? How will it do?
 do? It plays a principal role in It helps to measure 
designing  thermal the  spectral radiance 
Wien displacement law 
equipment for heating and  of emitted  thermal 
deals  with the spectral 
medical treatment radiations by  
radiance of  hot bodies 
purposes. quantifying their 
as a function of  their 
Mammals absorb and absolute  
wavelengths at a  
radiate  thermal energies to temperatures.
uniform temperature 
a large extent in  the far The sodium spectrum 
T. This  data helps to 
infrared regions at room  emits  two intense 
understand the  
temperature conditions of yellow-colored  D-
temperature at which 
25  degrees centigrade to 35 lines at 588.99 nm 
a  material can release 
degrees  Celsius. So, the and
highly  intense 
temperature of  heating 589.59 nm, indicating 
radiation.
equipment is adjusted  peak  intensified 
based on their requirement  spectral emissions  at 
following Wien law. approximately 5000 
Kelvin
temperature.
Final 
thoughts
How will What is its  When will it be 
it  work? limitation?  used?
It only calculates the  Though, Wien But in demanding 
maximum intense displacement  law situations,  its ease in 
spectral  emissions gives accurate results  calculating peak  
wavelength  released only for short-range  intense wavelengths of 
from a hot object at  wavelength  thermal 
its absolute measurements.  It is electromagnetic  
temperature  invalid at longer  radiations with their  
conditions. It is an  wavelength radiant  temperature data 
approximation emissions at the same makes it  convenient.
relationship  to relate  temperature 
a body's highest  conditions. So,  it 
emissive power with cannot apply to 
its  temperature. precise  
measurements of  
wavelengths of 
radiation.
For multiple choice 
questions
with answers on this 
topic,  kindly visit our 
blog article at;
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