Question

On observing light from three different stars $\text{P}$ , $\text{Q}$ and $\text{R}$ , it was found that intensity of violet colour is maximum in the spectrum of $\text{P}$ , the intensity of green colour is maximum in the spectrum of $\text{R}$ and the intensity of red colour is maximum in the spectrum of $\text{Q}$ . If $T_{p}, \, T_{Q}$ and $T_{R}$ are the respective absolute temperatures of $\text{P}$ , $\text{Q}$ and $\text{R}$ , then it can be concluded from the above observations that :

• A. $T_{P}>T_{Q}>T_{R}$
• B. $T_{P}>T_{R}>T_{Q}$
• C. $T_{P} < T_{R} < T_{Q}$
• D. $T_{P} < T_{Q} < T_{R}$

Answer 1

Answer: (B)

From Wein's Displacement law,
$\lambda _{m}T=constant \, \Rightarrow \lambda _{m} \propto \frac{1}{T} \, $
From the light spectrum,
$\left(\left(\lambda \right)_{m}\right)_{P} < \left(\left(\lambda \right)_{m}\right)_{R} < \left(\left(\lambda \right)_{m}\right)_{Q}$ (as $\lambda _{\text{Red}} > \lambda _{\text{Green}} > \lambda _{\text{Violet}}$ )
Hence,
$T_{P}>T_{R}>T_{Q}$