20150130

Online reading assignment: total internal reflection, polarization

Physics 205B, spring semester 2015
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on total internal reflection and polarization.

The reflection of the fish is upside-down.  Does that make sense?

Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"I understand that two conditions are required for total internal reflection to occur, including the ray of light in a higher refractive index material is incident on a material with a lower refractive index; and the incident angle in the higher refractive index material is greater than the critical value."

"Polarizers only allow polarized light to pass through if the polarized light matches the transmission axis of the polarizer."

"When particles oscillate in an unorganized fashion, the light emitted is unpolarized. On the other hand, a radio antenna would be a perfect example of a polarized light source, because the particles oscilate up and down in a vertical motion, such that the light will have vertical polarization."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"I found the 'frustrated refraction' concept very confusing. I had a hard time understanding the diagram that came with it."

"I have a hard time visualizing what is happening when reading the blog and textbook. I get mixed up when the text describes transmitted and incident angles and could use some examples or visual aids to picture how the light is reflecting on the higher and lower index materials. I think I am just getting mixed up with vocabulary."

"I'm not entirely sure how to draw the orientation of the transmitted polarized light."

If the incident angle of a light ray is less than the critical angle, the light ray will be:
reflected.  *** [3]
transmitted.  ************************ [24]
(Both of the above choices.)  ******** [8]
(Neither of the above choices.)  [0]
(Unsure/guessing/lost/help!)  *** [3]

If the incident angle of a light ray is greater than the critical angle, the light ray will be:
reflected.  ************************ [24]
transmitted.  ***** [5]
(Both of the above choices.)  ** [2]
(Neither of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  ****** [6]

Total internal reflection is possible when a light ray in a __________ medium hits a boundary with a __________ medium.
faster; slower.  ************* [13]
slower; faster.  ******************** [20]
(Both of the above choices.)  [0]
(Unsure/guessing/lost/help!)  ***** [5]

A vertical antenna will emit __________ polarized light.
horizontally.  ** [2]
vertically.  ***************************** [29]
(Both of the above choices.)  *** [3]
(Neither of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  *** [3]

Horizontally polarized light can be received by a _________ antenna.
horizontal.  ***************************** [29]
vertical.  ***** [5]
(Both of the above choices.)  [0]
(Neither of the above choices.)  [0]
(Unsure/guessing/lost/help!)  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Second week of school almost complete. Gosh how time flies when you are having fun doing physics."

"Please explain the differences between reflected, transmitted, and totally internally reflected rays...slowly." (O...k...a...y... Seriously, though, we'll keep doing more examples in class today.)

"Please go over polarization! And I though I understood the three different cases of total internal reflection...but now I'm questioning myself and need some clarification please!" (Yes, there will be enough time in class to follow up on questions you have on the reading assignment.)

"Will equations be given to us on quizzes and exam like last year?" (Yes, in fact the same set of equations that will be on the quizzes and exams are always listed on the last page of every worksheet packet.)

"Can you go over the practical applications section and the correct answers for these questions?" (As time allows, we can go over detailed solutions for the most problematic responses on the reading assignments. Also, don't forget that the answers to every reading assignment are posted the next morning on this blog (via Twitter hashtag #CuestaPhys205B).)

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