## 20150126

### Online reading assignment: electromagnetic waves, reflection and refraction

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 electromagnetic waves and redirecting light (reflection and refraction), along with advice from students from the previous semester, and videos on the flipped class mode of instruction used in this course.

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 electromagnetic spectrum covers all types of light, and visible light is only a very small portion. Different types of light differ by their frequency values, and radio waves have the lowest frequency, and gamma rays have the highest frequency."

"The difference between independent and dependent parameters when determining wavelength, speed, and frequency."

"Reflection is redirected light bouncing off a surface. Refraction is light passing through a transparent surface and is redirected by being 'bent.'"

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 don't understand why the light refracts the way it does as it passes between mediums. I understand that the light slows down, but not why that produces the effects that it does."

"I did not find anything confusing about the assigned reading or the presentation preview. Although it would be helpful to see the equations used in problems."

"The equation for index of refraction. Would it be possible to do some examples in class?"

"I'm having some difficulty with Snell's Law and the concept of how the transmitted ray can become manipulated. I know that it depends on the medium's index of refraction..but this all is a little too unclear for me."

Consider light traveling either through air (nair = 1.0) or through water (nwater = 1.33). Light travels with the faster speed through:
 air. *********************************** [35] water. ** [2] (There is a tie.) *** [3] (Unsure/guessing/lost/help!) ** [2]

A ray of light has an incident angle of 60° in air, and a transmitted angle of 36° in plastic. Determine what happens to each of the following parameters as the light passes from air into plastic.
(Only correct responses shown.)
speed v: decreases [71%]
frequency f: remains constant [55%]
wavelength λ: decreases [40%]

For the above example of light incident in air being transmitted into plastic, __________ has the greater index of refraction.
 air. *** [3] plastic. ******************************** [32] (There is a tie.) [0] (Unsure/guessing/lost/help!) ******* [7]

A ray of light has an incident angle of 20° in plastic, and a transmitted angle of 29° in air. Determine what happens to each of the following parameters as the light passes from plastic into air.
(Only correct responses shown.)
speed v: increases [60%]
frequency f: remains constant [52%]
wavelength λ: increases [40%]

For the above example of light incident in plastic being transmitted into air, __________ has the greater index of refraction.
 air. ************************** [26] plastic. ********* [9] (There is a tie.) * [1] (Unsure/guessing/lost/help!) ****** [6]

State your preference for denoting the inverse sine operation.
 Arcsin. *** [3] sin-1. ******************************* [31] (No preference.) ****** [6] (Unsure/guessing/lost/help!) ** [2]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I've learned that I need to keep myself updated on everything that happens in class and keep up with the homework and reading. There is no time to distract myself. Also how this course will be functioning from now on. Lecture time will be time to ask questions."

"I want to see some problems in class and show how to use the formulas in different problems, because sometimes I don't get what formula to plug in."

"Are questions from the reading assignments or the textbook more similar to your exam questions?" (Previous semesters' exam questions are similar to the exam questions you'll be seeing this semester. We'll go over them in class, and last year's exams are also posted on the course website.)