Science 421A
Name:
What is Light?
AnswerWhat desire by seventeenth century scientists fueled advances in early science?
The Story of Light
Watch Introduction video
Young’s Double-Slit Experiment
AnswerWhat were the two competing theories of light being debated by the end of the seventeenth century? Who were the supporters of each theory?
Messengers From Across the Ocean of Space
Explain How did the correct explanation for the nature of light come from an unlikely source?
DrawScottish physicist James Clerk Maxwell was Einstein’s hero. Clerk did what all great scientists do, he found the deep, true meaning of a natural phenomena. He saw that two things which appear to be unrelated were actually the same thing. This is called unification because it unifies two ideas into one and it is a major theme in the history of physics. Draw two flow charts that show the unification work of two great scientists. (You will have to think a bit for Newton. Remember how the early scientists and philosophers thought of earth’s place in the universe.)
Figure 2: Unification done by MaxwellFigure 3: Unification done by Newton
Chasing the Speed of Light
Answer What is the precise measurement for the speed of light? How many significant figures are in the measurement? Write the speed of light in scientific notation.
Answer What is the conversion factor from kilometers to light years?
Explain Why would Galileo bother to report “no result” to others after attempting to determine the speed of light? Wouldn’t he be worried about being seen as a failure?
Explain How did a societal need fuel advancements in determining the speed of light?
State What is your definition of speed?
Create Return to your “What is Time?” booklet. Look at the question in which you calculated the age of the Universe using Hubble’s Constant. Write the units for the constant below. Now think about how you used these units to find the age or the “time” of the Universe. Show how the formula for speed that can found using the units.
Investigate The measurement of the speed of light was the first determination of the value of what scientists call a “constant of nature.” These constants have special meaning for the properties of the Universe. What would a constant speed (like the speed of light) look like on a graph? Use a GLX and a motion sensor to create a position vs time graph for an object that is moving at a constant speed. (This means the position will be the dependent variable and time will be the independent variable)Note how the format for labeling Tables is different than that of Figures.
GraphUse your data from the GLX to graph the results.
Table 1: Position vs. Time for an object moving at a constant speed
Interpret Find the mathematical relationship that describes the shape of your graph.
CalculateFind the slope of the line in the graph. Show your work and be sure to include your units.
GraphWhat would a constant speed (like the speed of light) look like on a graph? Use the speed you calculated from your position vs time graph to create a speed vs time graph for an object that is moving at a constant speed.
Table 2: Speed vs. Time for an object moving at a constant speed
Time Travel
Watch and Explain Ask to view the Bob and Alice episode “Is That Star Really There?”
CalculateWhen you look at the sun you see it as it was 8 minutes in the past. Calculate the distance you are away from the sun. When you view Alpha Centauri in the night sky you see it as it was four years in the past, how far away is Alpha Centauri? Show your work.
The Birth of the Universe
Explain Why do scientists consider the WMAP a “baby picture” of the universe?
All the Colours of the Rainbow
StateWhat is the range of wavelengths that the human eye can detect? Don’t forget your units. Change the metric prefix into scientific notation.
The angstrom is not often used nowadays. It has been largely superseded by the nanometer (nm), which is 10 times larger; 1 nm = 10 angstroms = 10 -9 m.
Calculate
- 2000 m ____ Å
- 3900Å = ____ m
The Hubble Telescope
Watch Introduction video
Draw and Annotate Visit the course documents pages on the class website. Watch the video called “What is Light?” Recreate the diagram that Brian Cox draws on the chalkboard.Make sure you use the correct format for labeling Figures.