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Like the solar spectrum the spectra of stars show a continuous spectrum on which dark absorption lines are superimposed. The inner layer (called the photosphere) of the star emits radiations of all wavelengths, producing a continuous spectrum. When these radiations pass through the outer, relatively cooler, layer of the star, the radiation of certain wavelengths are selectively absorbed by this layer. This explains the dark lines in thespectrum of a star. The dark lines are characteristic of the substances present in the outer layer of the star.The surface temperature T of a star can be estimated by measuring the wavelengths λm at which the intensity of the emitted radiation is maximum and then using Wien's displacement law which states that λm x T = b where b is a constant called Wiens constant and the above relation is called Wiens Displacement Law which states that as the temperature increases, the maximum intensity of emission shifts (or is displaced) towards the shorter wavelengths. The value of constant b has been found experimentally to be 2.89 x 103mK .
In Wiens displacement law the SI unit of Wiens constant b is

A
metre per kelvin
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B
metre per kelvin square
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C
metre kelvin
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D
metre kelvin square
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Solution

The correct option is C metre kelvin
From the Wein's displacement law λmaxT=b,
Therefore S.I unit of b=λ×T
b=metre kelvin

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