Question

The ratio of temperatures of sun and moon, if the wavelengths of their maximum emission radiations rates are $140$ $Å$ and $4200$ $Å$ , will be

• A. $1:30$
• B. $30:1$
• C. $42:14$
• D. $14:42$

Answer 1

Answer: (B)

From Wien's law
${\lambda }_{m}T=constant$
Where ${\lambda }_m$ is maximum wavelength and $T$ is the absolute temperature.
Given, ${\lambda }_1=140Å$ , ${\lambda }_2=4200Å$
$\therefore$ $\frac{{\lambda }_1}{{\lambda }_2}=\frac{T_2}{T_1}=\frac{140}{4200}$
$\Rightarrow$ $\frac{T_2}{T_1}=\frac{1}{30}$
$\Rightarrow$ $\frac{T_1}{T_2}=\frac{30}{1}$