Question

The spectral emission power of a black body at $6000K$ is maximum at $5000\dot{A}$ . If the temperature is increased by $10\%$ then decrease in the value ${\lambda }_m$ will be

• A. 9.1 %
• B. 7.5%
• C. 5.0%
• D. 3.5%

Answer 1

Answer: (A)

9.1 %

According to Wein's displacement law:
$\lambda T=b$
when the temperature increases by $10\%$
the new temperature becomes 6600K
$5000\dot{A}\times 6000=\lambda \times 6600$
i.e. $\lambda =4545\dot{A}$
Change in wavelength $=455\dot{A}$
i.e. change in wavelength $=\frac{455}{5000}=10\%$