1. How is Stefan–Boltzmann law derived from Planck’s law of thermal radiation? What is the value of Stefan–Boltzmann constant? 2. Plot  vs. . What does the curve signify? 3. Explain how the...

1. How is Stefan–Boltzmann law derived from Planck’s law of thermal radiation? What is the value of Stefan–Boltzmann constant?

2. Plot
 vs.
. What does the curve signify?

3. Explain how the hemispherical emissivity of a real surface varies with wavelength, temperature, degree of roughness and degree of oxidation.