Relativity & Particle Mixing

The test will be a combination of long multiple choice, and essay questions. It will draw from all the topics we have covered in class, from physics ideas (e.g. how waves work), to specific experiment results (e.g. the interferometer demonstrated in class), to the history of measurement (e.g. development of clocks). To give you a feel for what a long multiple choice question will look like, the first HW question below is written in this style.

1)  How were the moons of Jupiter used to measure longitude?

a) The apparent positions of the moons of Jupiter depend on the angle you are observing Jupiter. The lunar orbits could be carefully calculated by astronomers (something that took months), and the predictions published in an almanac for the coming year. By observing the moons from a ship, one could consult the almanac and determine your longitude. 

b) On land or sea, a telescope can be used to observe when the moons were eclipsed by Jupiter (passed behind the planet). Because the observers in different locations are looking at Jupiter from a different angle, an observer to the east will see the eclipse earlier than an observer to the west. Recording the local time of the eclipse (based on the elevation of stars) allows an observer to calculate their longitude.

c) On land a telescope could be used to observe when the moons were eclipsed by Jupiter (passed behind the planet). Two observers in different locations will see the eclipse simultaneously. If they record the local time of the eclipse (based on the elevation of stars) and later compare their observations, the difference in local time will give them their separation in longitude. 

d) On land a telescope could be used to observe when the moons were eclipsed by Jupiter (passed behind the planet). Two observers in different locations will see the eclipse simultaneously. By noting which hour the eclipse happened the time zone the observers were in could be determined. The difference in time zone will give the separation of the observers in longitude.

The rest of these questions don’t have the multiple choice options, but could easily turned into long multiple choice questions. For the homework write a short but clear description of each.

2) The light from a red and a green laser are both observed with a sensitive detector than can observe how hard individual photons hit. Describe what the detector sees. 

3) We start with two observers, one on the earth and another on a spacecraft moving quickly away, both with light clocks. Describe what each observer sees. 

4) The light of two lasers of different colors are combined using a prism. Describe what you observe, and how it changes as the colors of the lasers are made more different (farther apart on the rainbow). 

5) The most common form of time is Coordinated Universal Time (UTC). Describe how UTC is related to atomic timekeeping and the rotation of the Earth.

And this last question is an example of an essay question as it might appear on the test.

6) Describe, as clearly as you can, how an optical clock works. 

Extra Credit:  Find and take a selfie at a reference baseline; the most accessible is 'Linehenge' at Magnusson Park