Question

A black body at 200 K is found to exit maximum energy at a wavelength 14 $\mu m$ . When its temperature is raised to 1000 K, then wavelength at which maximum energy emitted is :

• A. 14mm
• B. 7 $\mu m$
• C. 2.8 $\mu m$
• D. 28 mm

Answer 1

Answer: (C)

2.8 $\mu m$

Answer 2

From Weins displacement law ${{\lambda }_{m}}T=\text{constant,}$ Hence, ${{\lambda }_{m}}_{_{1}}{{T}_{1}}={{\lambda }_{{{m}_{2}}}}{{T}_{2}}$ So, ${{\lambda }_{{{m}_{2}}}}=\frac{{{\lambda }_{{{m}_{1}}}}{{T}_{1}}}{{{T}_{2}}}=\frac{14\times 200}{1000}=2.8\mu m$