Question

Why classical physics could not explain black body radiation?

Answer 1

The failure of Classical Physics to explain Black Body Radiation, the Photoelctric Current and the Hydrogen Atom ultimately demolished the foundations of Classical Physics. Max Plank, Albert Einstein, Niels Bohr and Louis de Brogile made inspired gusses about how does the nature works.

Answer 2

Black-body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature, called the Planck spectrum or Planck's law.