Question

The temperature of stars is determined by
(A) Stefan's law
(B) Wien's displacement law
(C) Kirchhoff's law
(D) Ohm's law

Answer 1

The temperature of the stars cannot be measured directly. It has to be determined by indirect means. The wavelength of the light obtained gives the idea about the temperature of the body. In our case, we measure the temperature with the help of the wavelength.

Complete step-by-step solution:
The Wien's displacement law states that the temperature of a black body is inversely proportional to the wavelength of the radiation emitted with maximum intensity by the blackbody. This can be written mathematically as:
$\lambda_m = \dfrac{1}{T}$ .
Therefore, as on earth, we observe the spectra of the radiation emitted by the star, we observe that a particular wavelength has maximum intensity. This wavelength directly gives the idea about the temperature of the star.
Therefore, the correct option here is option (B).
Additional information:
Blackbody radiation is an important phenomenon. Not only it tells about the relation of the temperature of the body with the energy density or the relation of the temperature with the wavelength of the body, but also it gives rise to the development of our understanding of particle nature of radiation. Planck's law was the first law ever that gave rise to this and helped in understanding the blackbody’s radiation in terms of particle natured radiation given out by the body.

Note: From the given set of options, the Kirchhoff's law and Ohm's law are applied in electronics, they are used to describe circuits. The Stefan's law is used to obtain the energy density of the radiation. It relates the energy density with the temperature of the body.