This chapter calls on trigonometry and calculus, both differentiation and integration.
In this chapter, we will see what happens when terahertz-frequency electromagnetic radiation encounters matter.
Imagine driving along a freeway. All the cars are travelling along at the same, high speed, 100 kmh. There is no stopping or turning on the freeway. (It is a little bit boring, really.) Then the freeway ends. The traffic slows, say to 60 kmh. Some cars pull over at the shops. Some cars turn off to the suburbs. Others continue through the town, and rejoin the freeway, and continue at 100 kmh.
No analogy is exact, but the cars on the freeway are something like light in a vacuum. In a vacuum, light travels at ...