Willhelm Wien

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Willhelm Wien

• Nobel Prize Winner 1911

For his discoveries regarding the laws governing
the radiation of heat
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A Brief History (For Further Information see your
Handout)

• Born on 13th January 1864 in East Prussia.
• Started School in 1879 and in 1882 went
• to the University of Gottingen to study
  Mathematics
• and the Natural Sciences.
• Appointed Professor of Physics at
  Aix-La-Chapelle
• in 1896
• Appointed to the same position at the University
  of
• Giessen in 1899
• In 1911 Wien won the Nobel prize for his work
• concerned with the radiation of heat.

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Why is Wien Important?

• He is responsible for the creation of the
• definition of Black Bodies.
• Wien developed a law which later became
• known as Wiens Displacement Law.
• Wiens other work made possible the
• calculation of factors relevant to Nuclear
• Reactions.

These developments of Wiens led to many advances
in Physics they allowed Astrophysicists to
measure the temperature of stars by their peak
emission
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What is a Black Body?

• A perfect absorber of radiation, absorbing 100
  of the
• radiation that strikes it. No reflection
  occurs, hence the
• term Black Body.
• A perfect emitter of radiation, radiating 100
  of that
• which it produces.

• Stars are a theoretical example of Black Bodies.

Demonstration of a Black Body Absorber
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Demonstration of a Black Body
Tin Can
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Development of Wiens Law

• The link between the temperature of a body
• and the wavelength of its peak emission

Peak emission measured using Spectroscopy

• Discovery that the wavelength of peak
• is inversely proportional to the temperature
• of the body

• Discovery of the constant of proportionality
• which links the two
• 2.9 10-3 m K

Such that
?max T A constant ( 2.9 10-3 m K )
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Wiens Law and the Electromagnetic Spectrum
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(Consult your hand-out for diagrams relevant to
this page)

• Wiens Law in reference to stars.
• Black Bodies that emit radiation appear
• different colours according to their
• temperature.
• Radiation emitted by the human body.
• Worked example using Wiens Law.