ACER 9/14 Lecture #3 Part 2: Introduction to Quantum Mechanics

What is Continuity?

The fundamental assumption of early science was the idea that nature is continuous, so any physical matter, including energy, can be measured, broken into, and changed by any infinitely small amount.

How does quantum mechanics deviate from the idea of continuity?

What proof is there?

The key theory of quantum mechanics is energy quantization, the idea that energy on an atomic level is not continuous and is instead quantized, so atoms can only absorb and emit energy in discrete packets called quanta.

The sharp, isolated lines on emission spectra show how energy is limited to discrete steps.

Strengths and Weaknesses of Classical/Newtonian Mechanics

Newtonian Mechanics are useful for explaining physics on a macro-level—for objects large enough that their quantum steps blend together to appear continuous. For example: the motion of planets and the kinetic theory of gases.

Newtonian mechanics cannot explain the behavior of objects as small as electrons.

What is a ‘blackbody’ and blackbody radiation?

Why was this concept created?

A blackbody is an idealized object that can perfectly absorb all light and re-emit that light (blackbody radiation) as thermal energy based on its temperature.

This concept was created to better understand incandescence.

The Ultraviolet Catastrophe (What was it and how was it resolved)

The math failure in classical mechanics that predicted as wavelengths shortened, the amount of energy emitted should approach infinity. Real-life blackbodies did not behave this way.

Planck resolved it by introducing quanta.