Question

A piece of iron is heated in a flame. It first becomes dull red, then becomes reddish yellow and finally turns to white-hot. The correct explanation for the above observation is possible by using-

• A. Newton's law of cooling
• B. Stefan's law
• C. Wien's displacement law
• D. Kirchhoff's law

Answer 1

The correct option is C Wien's displacement law

Wien's displacement law, gives the relation between temperature and wavelength $\left(\lambda \right)$

${\lambda }_{m}T=\text{constant}$

$\Rightarrow {\lambda }_m\propto \frac{1}{T}$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(C\right)$ is the correct answer.