Physics quiz question: polarized light transmitted through two polarizers

Physics 205B Quiz 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

Vertically polarized light is incident on a set of two ideal polarizers.


If the total fraction of the incident light intensity transmitted through both polarizers is 0.15, then the angle θ of the second polarizer is:
(A) 23°.
(B) 44°.
(C) 67°.
(D) 81°.

Correct answer (highlight to unhide): (C)

The fraction of the vertically polarized light that passes through polarizer 1 is cos²θ, where the angle θ = 0° is measured between the vertical polarization of the light entering polarizer 1, and the transmission axis of polarizer 1 (which is also vertical). The light after passing through polarizer 1, but before passing through polarizer 2 is still vertical (having a polarization that matches the transmission axis of polarizer 1).


The fraction of this vertically polarized light that passes through polarizer 2 is again cos²θ, where the angle θ measured between the vertical polarization of the light entering polarizer 2 and the transmission axis of polarizer 2 (rotated clockwise from the vertical) is unknown.


Since the total fraction of the light that passes through both polarizers is given, then this is the result of multiplying together the fractions that passed through each polarizer:

total fraction = (fraction 1)×(fraction 2),

0.15 = (1)×(cos²θ),

√(0.15) = cosθ

cos^–1(√(0.15)) = θ = 67.213502000402852°,

or to two significant figures, the clockwise angle θ that the transmission axis of polarizer 2 is rotated from vertical is 67°.

(Response (A) is cos^–1(√(0.85)); response (B) is (1/0.15)²; and response (D) is cos^–1(0.15).)

Student responses
Sections 30882, 30883
Exam code: quiz01PxP7
(A) : 2 students
(B) : 1 student
(C) : 30 students
(D) : 2 students

Success level: 86%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

Physics quiz archive: electromagnetic waves, polarization, reflection/refraction

Physics 205B Quiz 1, spring semester 2020
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz01PxP7



Sections 30882, 30883 results

0- 6 :	* [low = 6]
7-12 :	**
13-18 :	*********
19-24 :	*********** [mean = 21.9 +/- 5.9]
25-30 :	************ [high = 30]

Online reading assignment: polarization

Physics 205B, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a bi-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 re-reading textbook chapters and reviewing 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.

"In order for TIR to take place, two things must take place: the index of refraction for the first surface must be greater than the second, and the angle incident angle is less than the critical angle."

"Horizontal and vertical antennae didn't make sense to me at first, but after seeing a visual drawing of them, I understand how waves can be transmitted and received in certain directions, but also have dead zones in specific areas."

"A vertical antenna can send messages to other vertical antennas, and has a blind spot on the top and bottom."

"The fencepost model describes how light polarized in a specific direction can pass through a polarizer. Malus's law allows us to calculate how much polarized light passes through a polarizer."

"With polarized light, if the transmission axis of polarizer is perpendicular, all light is blocked. Light with polarization parallel to the transmission axis passes."

"How polarizing sunglasses work. All the molecular antennas have their own direction of polarization in the sunglasses so only half of unpolarized light gets through polarized sunglasses. I also liked learning about liquid crystal displays and the polarization of calculator displays."

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 think I understand the theory behind polarization but concepts are new and a little hard to wrap my head around."

"Having issues visualizing Malus' Law."

"I need more practice on angles other than 90° and 0° or 180°."

"I am still having a hard time grasping Malus' law and I am confused about about how polarized light and the transmission axis of a polarizer works."

"When light passes through multiple polarizers it gets more confusing."

"Honestly it all seemed overwhelming and confusing. if the basics are covered I am pretty sure I'll understand it."

How much unpolarized light is transmitted through an ideal polarizer?

0%.	* [1]
50%.	********************************** [34]
100%.	* [1]
(Unsure/guessing/lost/help!)	* [1]

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%.	********************* [21]
50%.	****** [6]
100%.	****** [6]
(Unsure/guessing/lost/help!)	**** [4]

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.	*** [3]
vertical.	************************ [24]
diagonal, upper left to lower right.	* [1]
diagonal, lower left to upper right.	*** [3]
(Unsure/guessing/lost/help!)	****** [6]

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.	******************* [19]
vertically polarized.	*************** [15]
diagonally (upper left to lower right) polarized.	[0]
diagonally (lower left to upper right) polarized.	[0]
unpolarized.	[0]
(Unsure/guessing/lost/help!)	*** [3]

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.	***** [5]
vertically polarized.	********** [10]
diagonally (upper left to lower right) polarized.	*** [3]
diagonally (lower left to upper right) polarized.	************ [12]
unpolarized.	*** [3]
(Unsure/guessing/lost/help!)	**** [4]

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

"Please review answers to above questions."

"I think I need some clarification on the difference between polarized and unpolarized light in class if possible."

"Is diagonally polarized light a thing?" (Yes, definitely.)

"Why do screen manufacturers polarize screens in different ways? Why wouldn't there be an industry standard?"

"Does unpolarized light correspond to bright light? Can polarized light be as bright as unpolarized?" (Yes. Glare off of water or ice is mostly polarized, but polarizing sunglasses can help cut that down.)

"Book is here. Book is unread." (An unread book is a dead book.)

"Have you been to Pismo Preserve yet? The trails were really nice this weekend." (Not yet. #fomo.)

Physics midterm question: same transmitted fraction of unpolarized/polarized light

Physics 205B Midterm 1, spring semester 2019
Cuesta College, San Luis Obispo, CA

In case (a) unpolarized light is incident on a 45° diagonal polarizer, and a certain fraction of incident light is transmitted through it. For case (b) horizontal polarized light is incident on a polarizer with a transmission axis that can be rotated to any θ angle. Discuss what the θ angle should be in case (b) such that the same fraction of incident light is transmitted through it as in case (a). Explain your reasoning using the properties of light and polarization.

Solution and grading rubric:

• p:
  Discusses/demonstrates that:
  1. in case (a), the fraction of unpolarized light that passes through a polarizer (regardless of its transmission angle) is (1/2); and
  2. for case (b), the fraction of polarized light that passes through a polarizer is given by Malus' law: cos²(90° − θ), where the angle of interest is between the horizontally polarization of the incident light and the transmission angle of the polarizer; and
  3. for the fraction transmitted in case (b) to equal the fraction transmitted in case (a), sets cos²(90° − θ) = (1/2), and thus θ = 45°.
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete. At least understands what happens in case (a), and has some systematic approach to match this fraction for case (b).
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying the properties of light, polarizers, and polarization.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying the properties of light, polarizers, and polarization.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01Ft6G
p: 16 students
r: 2 students
t: 14 students
v: 10 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7843):

Physics quiz question: polarized light transmitted through two polarizers

Physics 205B Quiz 1, spring semester 2019
Cuesta College, San Luis Obispo, CA

Polarized light passes through two polarizers with polarization axes turned as shown below.


The total fraction of the incident light intensity transmitted through both polarizers is:
(A) 0.017.
(B) 0.063.
(C) 0.23.
(D) 0.87.

Correct answer (highlight to unhide): (A)

The fraction of the diagonally polarized light that passes through the polarizer 1 is cos²θ, where the angle θ = 75° is measured between the horizontal polarization of the light entering polarizer 1, and the transmission axis of polarizer 1 (15° clockwise from vertical). The light after passing through polarizer 1, but before passing through polarizer 2 is now diagonally polarized, having a polarization that matches the transmission axis of polarizer 1 (15° clockwise from vertical).


The fraction of this diagonally polarized light that passes through polarizer 2 is again cos²θ, but where the angle θ = 60° is measured between the diagonal polarization of the light entering polarizer 2 (15° clockwise from vertical) and the transmission axis of polarizer 2 (15° counterclockwise from the horizontal).


Thus the fraction of light that passes through both polarizer 1 and polarizer 2 is:

cos²(75°)·cos²(60°) = (0.067)⋅(0.25) = 0.017,

of the original unpolarized intensity, to two significant figures.

(Response (B) is cos²(75°)·cos²(15°); response (C) is cos²(15°)·cos²(60°); and response (D) is cos²(15°)⋅cos²(15°).)

Student responses
Sections 30882, 30883
Exam code: quiz01aN7u
(A) : 11 students
(B) : 12 students
(C) : 3 students
(D) : 11 students

Success level: 32%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

Physics quiz archive: electromagnetic waves, polarization, reflection/refraction

Physics 205B Quiz 1, spring semester 2019
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz01aN7u




Sections 30882, 30883 results

0- 6 :	* [low = 3]
7-12 :	****
13-18 :	*******
19-24 :	***************** [mean = 20.8 +/- 5.7]
25-30 :	******** [high = 27]

Online reading assignment: polarization

Physics 205B, spring semester 2019
Cuesta College, San Luis Obispo, CA

Students have a bi-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 re-reading textbook chapters and reviewing 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.

"The direction of disturbances, perpendicular to the direction of the wave, determine the polarization of the wave. An example of polarized light source is an antenna."

"When atoms and electrons, sources of light, vibrate in different directions, they generate unpolarized light. In contrast with antennas, electrons have to move up and down the length."

"Waves that are linearly polarized can only pass through openings that are parallel to the direction of the rope vibrations. A polarizing material is called a polarizer."

"I felt like I really grasped the idea of the fencepost models we were given and how when unpolarized light is incident on a polarizer, only the light parallel to the polarizer will pass through.The light that passes through will have a polarization direction that matches the transmission of the polarizer."

"I understood that all light will pass through a polarizer if the transmission axis and polarization of the incident light are parallel. In contrast, if the polarization of the transmission axis and incident light are perpendicular, no light will pass through."

"Light that is perpendicular to a polarizer is not transmitted. The intensity of light that passes through a polarizer is related to the angle of the polarizer to the transmission axis of the light. The intensity of light transmitted is equal to the intensity of light entering the polarizer multiplied by the square of the cosine of the angle of the polarizer."

"Malus' law is a way to determine the intensity of polarized light after it goes through a polarizer and is filtered. Cos²θ of the unpolarized light going through a polarizer will give you the new intensity of the polarized light."

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 am confused as to why east-west oriented antennae are best transmitted north-south. What causes this?"

"I'm not quite understanding how it is that electrons can move side to side along a horizontal antenna."

"I find it confusing when unpolarized light passes through several stacked polarizers ( how the polarization of the polarizers affects the light)."

"Unpolarized light could be a little confusing. I also found some of the questions a bit confusing."

"I do not fully understand how to structure information about polarizers to solve questions about the intensity of light. I would benefit from examples on how to use Malus' law."

"I don't quite understand the LCD screen section. I would like to understand more about how voltage works. It makes sense to me that light is one type of electromagnetic wave but I am confused about how it relates to the positive and negative charges on the transparent electrodes sandwiching the liquid crystal. I also don't quite understand how the liquid crystal works and if it is related to solid crystal."

How much unpolarized light is transmitted through an ideal polarizer?

0%.	**** [4]
50%.	*********************** [23]
100%.	***** [5]
(Unsure/guessing/lost/help!)	***** [5]

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%.	******************** [20]
50%.	******** [8]
100%.	**** [4]
(Unsure/guessing/lost/help!)	***** [5]

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.	*** [3]
vertical.	**************** [26]
diagonal, upper left to lower right.	*** [3]
diagonal, lower left to upper right.	[0]
(Unsure/guessing/lost/help!)	***** [5]

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.	******************* [19]
vertically polarized.	********** [10]
diagonally (upper left to lower right) polarized.	* [1]
diagonally (lower left to upper right) polarized.	** [2]
unpolarized.	[0]
(Unsure/guessing/lost/help!)	***** [5]

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.	******* [7]
vertically polarized.	********* [9]
diagonally (upper left to lower right) polarized.	***** [5]
diagonally (lower left to upper right) polarized.	[11]
unpolarized.	[0]
(Unsure/guessing/lost/help!)	***** [5]

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

"This section is making sense to me and I find it very interesting because I've always wondered what polarized sunglasses did. I think all of the concepts make sense to me so far but I do have a couple questions about polarized light. For one, I am having a hard time understanding the energy of light and basically how it is created. It just seems weird to me how antenna's shoot electrons up and down to create a wave out of thin air? What are these waves made of? How do they keep energy and are able to travel so far?"

"I like this section but I wish there was more explanation of how light waves are formed, and what they are. I understand the concepts but it would be cool to get deeper understanding of how it all works. For example if I wanted to create and antenna and start sending out waves I would have no idea where to start." (Wait until we get through electromagnetism, as light waves are just oscillating electromagnetic fields.)

"What makes a material capable of polarizing light?" (Something that looks like fencepost on the scale of light wavelengths. A set of parallel metal rods will polarize radio waves, while a sheet with long, parallel polyvinyl alcohol chains will polarize visible light.)

"If something is polarized, that means light only transmits in a single direction? If sunglasses are polarized, that means that only single direction of light can transmit through?" (Yes.)

"I am confused about the two polarizer filters lined up and how much unpolarized light is able to get through. If only 50% gets in through the first one and the second filter is lined up on the same axis then would 50% be the final amount that gets through and if the second filter is lined up on a perpendicular axis it would be 0%?"

"Could you go into these sunglasses examples especially the one with the Nexus smartphone?"

"I'm kind of struggling on this subject."

Physics midterm question: different light polarizations, same polarizer set

Physics 205B Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

A set of two polarizers has either (a) horizontally polarized light, or (b) vertically polarized light incident on it. Discuss why this set of two polarizers will pass through the same fraction of horizontally polarized and vertical polarized light. Explain your reasoning using the properties of light and polarization.

Solution and grading rubric:

• p:
  Discusses/demonstrates that the same amount of light will pass through the set of polarizers as:
  1. the horizontally polarized light is at an angle of 45° with respect to polarizer 1, resulting in cos²45° = (1/2) of this passing through, with a 45° polarization angle parallel to that of polarizer 1; and
  2. the vertical polarized light is also at an angle of 45° with respect to polarizer 1, resulting in cos²45° = (1/2) of this passing through, also with a 45° polarization angle parallel to that of polarizer 1; then
  3. since for both cases (initially horizontally polarized light or initially vertically polarized light) the light that has passed through polarizer 1 has the same polarization angle and intensity, after passing through polarizer 2 the amount of light (and polarization direction) will be same for both cases.
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: midterm01cVdP
p: 26 students
r: 3 students
t: 4 students
v: 0 students
x: 0 students
y: 0 students
z: 0 student

A sample "p" response (from student):

Physics quiz question: polarized light transmitted through two polarizers

Physics 205B Quiz 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

Polarized light passes through two polarizers with polarization axes turned as shown below.


The total fraction of the incident light intensity transmitted through both polarizers is:
(A) 0.
(B) 0.19.
(C) 0.38.
(D) 0.56.

Correct answer (highlight to unhide): (B)

The fraction of the diagonally polarized light that passes through the vertical polarizer 1 is cos²θ, where the angle θ = 60° is measured between the diagonal polarization of the light entering polarizer 1 (60° clockwise from vertical) and the transmission axis of polarizer 1 (vertical). The light after passing through polarizer 1, but before passing through polarizer 2 is now vertically polarized, having a polarization that matches the transmission axis of polarizer 1.


The fraction of this vertically polarized light that passes through polarizer 2 is again cos²θ, but where the angle θ = 30° is measured between the polarization of the light entering polarizer 2 (vertical) and the transmission axis of polarizer 2 (30° counterclockwise from the vertical).


Thus the fraction of light that passes through both polarizer 1 and polarizer 2 is:

cos²(60°)·cos²(30°) = (1/4)⋅(3/4) = (3/16) = 0.1875,

or to two significant figures, 0.19 of the original unpolarized intensity.

(Response (C) is (1/2)·cos²(30°), which would be the fraction of unpolarized light that would pass through both polarizers; and response (D) is cos²(30°)⋅cos²(30°).)

Student responses
Sections 30882, 30883
Exam code: quiz01AM0l
(A) : 4 students
(B) : 25 students
(C) : 5 students
(D) : 1 student

Success level: 71%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.45

Physics quiz archive: electromagnetic waves, polarization, reflection/refraction

Physics 205B Quiz 1, spring semester 2018
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz01AM0l




Sections 30882, 30883 results

0- 6 :
7-12 :	* [low = 9]
13-18 :	****
19-24 :	**********
25-30 :	************** [mean = 24.7 +/- 4.9] [high = 30]

Online reading assignment: polarization

Physics 205B, spring semester 2018
Cuesta College, San Luis Obispo, CA

Students have a bi-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 re-reading textbook chapters and reviewing 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.

"Polarization has been easier to understand from the presentation and in class activities. Based on the way the antenna or whatever transmission device is facing, polarization will occur neither above or below, but alongside it."

"In all honesty I found this material unclear without an instructor's explanation. Extra help and clarification is needed."

"The lesson was pretty easy to understand regarding the function of antennas and their waves. The use of vertical and horizontal antennas have different uses such as for airplanes or old fashion televisions."

"The fence model example to describe polarization is VERY helpful. Makes the concept easy to imagine/see."

"Only about half of the original intensity of unpolarized light is able to pass through a polarizer. Meanwhile the remaining light is vertically polarized with another half of polarized light."

"Light polarization can be studied through interaction between antennae and polarizers. Light emitting from a glowing phenomenon, like molten lava, is unpolarized--oscillating in all directions, whereas an antenna is polarized (vertical waves). Incident light polarization can be calculated by the angular orientation of the polarizer. A polarizer set perpendicular to the wave will have a transmission of zero, as cosine²(90°) is zero. Incident light from a vertical antenna passing through a vertically-oriented polarizer will have essentially full transmission (cosine²(0°))."

"The introduction to polarization in general terms. I understand antennas much better as far as knowing what direction they should be for signal reception."

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.

"Polarization is confusing in my opinion. I feel with some extra explanation I'll understand."

"Malus' law is confusing. Especially when the transmission axis polarizer is at arbitrary angle to the polarization of incident light."

"Thinking through the specific polarization(s) of light that would be blocked."

"I feel as though I understand most of this material. But I could use some better explanation on how the angle of unpolarized light going through a polarized surface, how you are able to calculate the amount of light making it through."

"Double layers of polarization."

"I had a little more difficulty understanding the fencepost model. Specifically the relationship between the direction of light and the fenceposts."

How much unpolarized light is transmitted through an ideal polarizer?

0%.	****** [6]
50%.	********************** [22]
100%.	* [1]
(Unsure/guessing/lost/help!)	** [2]

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%.	******************** [20]
50%.	******* [7]
100%.	* [1]
(Unsure/guessing/lost/help!)	*** [3]

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.	******* [7]
vertical.	********** [20]
diagonal, upper left to lower right.	[0]
diagonal, lower left to upper right.	* [1]
(Unsure/guessing/lost/help!)	*** [3]

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.	******************* [19]
vertically polarized.	*********** [11]
diagonally (upper left to lower right) polarized.	[0]
diagonally (lower left to upper right) polarized.	[0]
unpolarized.	* [1]
(Unsure/guessing/lost/help!)	[0]

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.	*** [3]
vertically polarized.	********* [9]
diagonally (upper left to lower right) polarized.	**** [4]
diagonally (lower left to upper right) polarized.	*********** [11]
unpolarized.	** [2]
(Unsure/guessing/lost/help!)	** [2]

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

"Would radio waves be blocked better by some building materials than others?" (Yes, if an insulating material is really thick, or by a thin layer of conducting material (which is a better receiver of radio waves, and so would "subtract" out radio waves.)

"Not sure I understand when light passes through the first polarizer and get blocked by the second one."

"I'm good as long as we go over polarizers in detail."

"Could you go over Malus' law and the last part of the polarization section of the presentation preview?"

"Polarizing directions are confusing."

"Coming to office hours when I am too confused really helps."

"I am really glad that you are instructing our lab sessions. I feel much more secure in class."