A small cavity of volume 4 x 10⁻⁶ m³ is heated at 2000K. Calculate the energy density in the wavelength region 400 nm to 430 nm.
a) 4.97 x 10⁻¹⁶ J/m³
b) 3.71 x 10⁻¹⁶ J/m³
c) 6.42 x 10⁻¹⁶ J/m³
d) 8.15 x 10⁻¹⁶ J/m³