Sun's surface at 5800 K emits radiation at a wavelength of 0.5$\mu$. A furnace at 300°C will emit through a small opening, radiation at a wavelength of
- A. 5$\mu$
- B. 0.5$\mu$
- C. 2.5$\mu$
- D. 0.25$\mu$
Answer: A. 5$\mu$
Explanation: Wien's Law: $\lambda_1 T_1 = \lambda_2 T_2$. $0.5 \times 5800 = \lambda_2 \times (300+273)$. $2900 = \lambda_2 \times 573 \Rightarrow \lambda_2 \approx 5.06 \mu m$.