Lesson Plan

Describe a blackbody and interpret the blackbody radiation spectrum (intensity vs. wavelength)

Explain the ultraviolet catastrophe as a failure of classical physics

State that energy is quantized and use E = nhf to calculate the quantum energy of light

Calculate the number of photons emitted per second from a light source of given power

Explain how photon energy varies across divisions of the electromagnetic spectrum and why quantization is not observed in everyday life

21.1

"A perfect blackbody is one that absorbs and re-emits all radiated energy that is incident upon it." "The disconnect between theory and reality was termed the ultraviolet catastrophe." "This theory, which created the branch of physics called quantum mechanics, speculated that the energy radiated by the blackbody could exist only in specific numerical, or quantum, states. This theory is described by the equation $E = nhf,$ where n is any nonnegative integer (0, 1, 2, 3, …) and h is Planck's constant, given by $h = 6.626 \times 10^{-34}\ \text{J·s},$ and f is frequency." "Atoms, molecules, and fundamental electron and proton charges are all examples of physical entities that are quantized—that is, they appear only in certain discrete values and do not have every conceivable value."