This part of "Stargazers" assumes the reader is already familiar with sections
(S-4) The Many Colors of Sunlight
(S-5) Waves and Photons
From here one can continue with sections on the Sun, its energy and related sections on nuclear energy. All these provide a reasonably comprehensive, non-mathematical introduction to solar-related physics, at the level of high school or beginning college.
However... whereas rest of "From Stargazers to Starships" revolves around Newton's laws of motion and their applications, Sun-related physics is frequently concerned with the physics of the atom and nucleus, where those laws are greatly modified.
Like Newtonian mechanics, "quantum mechanics" is a mathematical field, but even its basic applications demand much more mathematics. Its coverage here is therefore very much simplified. Do not expect "Stargazers" to teach you quantum physics: the most these web pages can do is give a quick survey of its origins, and sketch out some basic ideas. You will learn what the main components are, and a bit about the way they evolved, but to do more, you will have to fill those empty boxes with solid, mathematical knowledge.
This is optional material: if you skip it and continue, you may still get a fairly coherent picture.
Einstein's 1905 formula (see here)
E = hν
was an early indication that on the atomic scale the laws of physics were quite different. Furthermore, it suggested that the new laws were intimately connected with a new physical constant, now known (for reasons discussed below) as "Planck's constant" h. To an accuracy of 6 decimals
h = 6.626068 10–34 joule-sec;