Light is the visible part of the electromagnetic spectrum. Electromagnetic waves like light exhibit all the phenomena of waves that we have already learned about.

Because electromagnetic waves are transverse waves, they can can have vertical or horizontal polarization.

When an electron falls from a higher energy level in an atom to a lower energy level in an atom, it gives off a photon with an energy equal to the change in the two energy levels. The energy corresponds to a specific wavelength, frequency, and color. The emission spectra of an atom is all of the colors that corresponds to energy level transitions in that atom. The only photons that will be absorbed by an atom are the ones that match energy level transitions, so atoms also have absorption spectra. These spectra, along with Doppler shift, can be used to measure the velocity of an object in space moving towards us or away from us.

The direction that light is moving can be changed through reflection or refraction. Light bends from refraction because light travels slower in denser materials. As it crosses the boundary from air to water the direction is changes, just like driving from pavement to sand at an angle would change the direction a car travels.

Refraction and reflection can be used to making different kinds of optics like lenses. A lens bends light in a way that is useful, allowing us to see things as larger than they really are.

For many years scientists couldn't figure out if light was made from waves or from particles. Refraction and Young's Two-Slit experiment can only be explained if light is made of waves, but the photoelectric effect can only be explained if light is particles.

It turns out that not only light has the characteristics of both waves and particles, but everything does! That means that the atoms that make up your body can be thought of as waves. This starts to get into the realm of quantum mechanics. When I took Intro to Quantum Mechanics in college my professor started his first lecture by saying “At the end of this course you will all be very disturbed.” He was right!


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Reflection and Refraction (AL)