This assignment, like last week’s, is in two parts. The first part is more practice making HTML files, and the second is a menu of physics questions.
This week’s HTML tutorial, Stylesheets And Classes, describes more advanced ways to dress up HTML files. Read it. You may some day want to use the things it teaches.
Once you have read the tutorial, try out some of the techniques it describes. I’m not going to require any particular tricks; this is just to make sure that you are able to display information the way that you want.
Last week’s tutorial described how to display graphics. It may be a good idea to go back to that lesson and make an HTML file that displays a graphic. Because you may not be able to post graphics on the web (unless you belong to Flickr or a similar photo-sharing site), and because hot-linking to photos on the web without permission is impolite, I have posted several photos to my web site that you are welcome to reference. The page barransclass.com/shared_pix/shared_photos.html displays the photos along with their URL’s. You may reference any of them in your file, or you may reference any graphics file for which you have permission.
Name your HTML file as “HW08_Lastname_Firstname.html.” For example, if I were to do this exercise, I would name the file “HW08_Barrans_Richard.html.”
If you are able to make your HTML file do everything you want it to, that is terrific! If you run into problems, please upload what you have to this assignment in Sakai. I can look at it, offer advice, and even upload a “corrected” version for you to see if appropriate.
Answer one, and only one, of the following questions.
These questions are for you to combine different ideas from the unit and apply them to situations not directly addressed in class or in the textbook. Think about the situation, and about the physics that applies to it. See me for help if you are stuck.
Human eyes have three different color receptor cells. Birds and reptiles, on the other hand, have four, sensitive to a greater range of wavelengths of light than ours. (For more information, read “What Birds See” by Timothy H. Goldsmith on pp. 68–75 of the July 2006 issue of Scientific American.) How and why would color printing and computer monitor displays need to be different if humans had eyes like birds instead of the pathetic peepers we’re stuck with?
When you look into a flat mirror straight-on, you see your reflection. Why? What is happening to make it appear that someone who looks like you is standing behind the mirror? (Drawing a sketch may help you explain. See me if you need help converting your drawing to a computer graphics file.)
Explain how additive and subtractive colors work. (Computer monitors use the additive color scheme, with the three primary colors red, green, and blue; printers use the subtractive color scheme, with the three primary colors cyan, magenta, and yellow.) Your answer should include:
The gas discharge tubes you observed in Activity 1 emitted light of only a few discrete wavelengths, so that their spectra consisted of mostly darkness with a few bright, narrow lines. The incandescent light bulb, on the other hand, emitted light of many different wavelengths, so that its spectrum was a broad smear of all visible wavelengths. How are the different colors of light created in the two cases, and why are the spectra so different? Specifically explain:
Glass prisms, and other faceted clear objects such as cut diamonds and cut glass pendants, scatter light into colored patterns. One of your third-grade students notices this and asks you why that happens. How do you explain it to her?
Your answer should be a script of the dialogue between the student and you. It should consist of exactly what each of you say, and stage directions if appropriate.
You may submit your entire response as a single HTML file. Or, you may submit the whole thing as hard copy or an electronic document. (However, I don’t recommend that because it will not give you practice with HTML.) Or, you may submit part 1 as an HTML file and part 2 as a hard copy or an electronic document. Remember to name your HTML file as specified.
If you submit any part of this assignment as an HTML file or an electronic document, upload it (or them) to Sakai using the “Assignments” tool. That way I will be able to find them easily and I will not tend to lose them.
Copyright © 2006, Richard Barrans
Revised: 10 October 2011. Maintained by Richard Barrans.
URL:http://www.barransclass.com/phys1090/hw/hwk08_light.html