Online reading assignment: polarization

Physics 205B, spring semester 2014
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 polarization.

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 feel a little more comfortable with the TIR material from the homework. I somewhat understand the polarization concept because of that Terminator 2 reference, i.e. things must go or move in a certain orientation to work or fit."

"Polarization is the generating and transmitting light using antenna and filters. Polarizers transmit light either horizontally-horizontally or vertically-vertically. Light that is traveling horizontally through a vertical plane will not pass through."

"Light waves can only be transmitted and received with matching antennae."

"I believe I understand what a transverse wave is, as well as unpolarized and polarized light source. Unpolarized light source is also known as randomly polarized, which is when the electric field changes frequently and the charges vibrate in random directions. Polarized light source is an example of a radio antenna in which electrons are forced to follow a specific length or area in vertical or horizontal 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.

"How are radio waves generated horizontally/vertically?"

"I'm kind of confused on how to use the equations...as always."

"I don't understand how to apply Malus' law. I also don't understand the horizontal antenna example in the lecture presentation."

A horizontal antenna will emit __________ polarized light.

horizontally.	***************************** [29]
vertically.	******* [7]
(Both of the above choices.)	** [2]
(Neither of the above choices.)	[0]
(Unsure/guessing/lost/help!)	*** [3]

Vertically polarized light can be received by a _________ antenna.

horizontal.	******* [7]
vertical.	***************************** [29]
(Both of the above choices.)	* [1]
(Neither of the above choices.)	* [1]
(Unsure/guessing/lost/help!)	*** [3]

How much unpolarized light is transmitted through an ideal polarizer?

0%.	******** [8]
50%.	********************** [22]
100%.	***** [5]
(Unsure/guessing/lost/help!)	****** [6]

Unpolarized light shines through two ideal polarizing sheets, that have their transmission axes aligned at right angles to each other. How much of the original intensity is transmitted through these two sheets?

0%.	*************** [15]
50%.	************ [12]
100%.	* [2]
(Unsure/guessing/lost/help!)	************ [12]

Unpolarized light is projected through the first (smaller) polarizer. If the transmission axis of this first polarizer is horizontal, then one-half of the unpolarized light will pass through, and the light that passes through is now horizontally polarized.

When the light that passed through the first polarizer is now completely blocked by the second polarizer, the transmission axis of the second polarizer is:

horizontal.	********* [9]
vertical.	******************* [19]
diagonal, upper left to lower right.	****** [6]
diagonal, lower left to upper right.	** [2]
(Unsure/guessing/lost/help!)	******** [8]

Polarizing sunglasses are typically manufactured with a vertical transmission axis (to filter out horizontally polarized glare while fishing or driving).

Light from the screen of the iPad (in portrait mode) is:

horizontally polarized.	************* [13]
vertically polarized.	********* [9]
diagonally (upper left to lower right) polarized.	*** [3]
diagonally (lower left to upper right) polarized.	* [1]
unpolarized.	** [2]
(Unsure/guessing/lost/help!)	******** [8]

Consider a Nexus 4 smartphone (again, held in portrait mode), and polarizing sunglasses (with a vertical transmission axis).

Light from the screen of the Nexus 4 is:

horizontally polarized.	**** [4]
vertically polarized.	******** [8]
diagonally (upper left to lower right) polarized.	******** [8]
diagonally (lower left to upper right) polarized.	******** [8]
unpolarized.	[0]
(Unsure/guessing/lost/help!)	******** [8]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"None at the moment."

"So our vertical car antennas receive vertical radio waves?" (Yes!)

"What causes polarization exactly? Is it the arrangement of the molecules that allow the light to pass through in a certain orientation?" (Yes; especially if the molecules form long chains that align with each other.)

"How can you tell if light is horizontally polarized, vertically polarized, or diagonally, etc.?" (You will need a polarizing filter to tell you this.)