(b) $\lambda_{m} \propto \frac{1}{T} \Rightarrow \lambda_{m_{1}}T_{1} = \lambda_{m_{2}}T_{2}$ $\Rightarrow T_{2} = \frac{\lambda_{m_{1}}T_{1}}{\lambda_{m_{2}}} = \frac{1.4 \times 10^{- 6} \times 1000}{2.8 \times 10^{- 6}} = 500\ K$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.