A small cavity of volume 4 × 10⁻6 m³ is heated to 2000 K. Calculate the energy density in the wavelength region from 400 nm to 430 nm.
a) 3.21 × 10⁷ J/m³
b) 2.86 × 10⁷ J/m³
c) 5.92 × 10⁷ J/m³
d) 7.45 × 10⁷ J/m³