29.1 Quantization of Energy

Everything is built of multiple substructures.
The branch of physics that deals with small objects and quantization is called quantum physics.
Similar to classical physics, quantum physics has several subfields, such as mechanics.
We begin the development of quantum mechanics in this chapter.
We will look at atomic and nuclear physics in later chapters, in which quantum mechanics is important.

The classical case is different because the system can only have certain energies and not a continuum.

It would be similar to having only certain speeds at which a car can travel.
Some forms of energy transfer take place with small amounts of energy.
Most of us are familiar with the quantization of matter into small particles called atoms, but we don't know that energy can also be quantized.
The quantization of energy was one of the earliest clues about the necessity of quantum mechanics.

The solid's temperature is linked to the EM spectrum.
An ideal radiator has an emissivity of 1 at all wavelengths and is jet black.
The total intensity of the radiation varies depending on the fourth power of the body's temperature and the peak of the spectrum shifts to shorter wavelengths at higher temperatures.
The curve of the spectrum of intensity versus wavelength gave a clue that the atoms in the solid are quantized.
At the turn of the century, providing a theoretical explanation for the measured shape of the spectrum was a mystery.
The answers to the "ultraviolet catastrophe" led to the development of new technologies such as computers.
The way we live was changed by physics.

The German physicist Max Planck used the idea that atoms and molecules in a body emit and absorb radiation.

To describe the shape of the blackbody spectrum, the energies of the oscillating atoms and molecules had to be quantized.

This is a pendulum that can swing with certain frequencies, but only with certain frequencies.
The quantization of energy is similar to a standing wave on a string.
It is similar to going up and down a hill using stair steps rather than being able to move up and down a continuous slope.
As you move from step to step, your potential energy takes on some values.

Planck was able to describe the blackbody spectrum using the quantization of oscillators.

This was the first time that quantization of energy on a small scale earned him a prize.
The analysis of Planck's theory is based on atoms and molecules.
It was such a departure from classical physics that Planck was reluctant to accept his own idea that energy states are not continuous.
Einstein's explanation of the photoelectric effect, which took energy quantization a step further, greatly enhanced the general acceptance of Planck's energy quantization.

Einstein's special relativity was published in 1905 and the first formula for relativistic momentum was suggested in 1906 by Planck.

The first to recognize that energy is sometimes quantized is the German physicist Max Planck.

Special relativity and classical physics were made by Planck.
The difference between energy levels is only about 0.4 eV for a blackbody emitting an IR Frequency.
This 0.4 eV of energy is significant compared with typical atomic energies, which are typically fractions of an electron volt.
On a classical scale, the energies are usually on the order of joules.
The quantum steps are too small to be noticed.
The correspondence principle is used in this example.
The results of classical physics are indistinguishable from those of quantum mechanics.

The Sun is one of the most common examples of a body emitting gases and visible light.
Neon signs and candle flames are examples.