20130224

Online reading assignment: interference

Physics 205B, spring semester 2013
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 interference.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"If you don't plug stereo cords in their appropriate color inputs the waves as a result will oscillate out of phase and not align which why it won't produce a sound."

"How switching polarities of a speaker can in theory silence the sound, but in reality just reduce the sound."

"How destructive and constructive waves work, my brothers are both in bands and when they are setting up the amps I always wonder why so many cords are necessary."

"It's interesting to think about the application of sound waves and how they work and can interfere with each other. I DJ and you deal with that all of the time."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The use of the equations for interference. I am getting lost with the equations."

"I found the equations for constructive and destructive interference confusing! We should use them in an example in class!"

"I was a little confused on what exactly constructive and destructive interference were. Is constructive when sound is produced and destructive silence?"

"What exactly happens when two speakers are set up so the sound waves are perfectly destructive? They create silence?"

"I read the portion about constructive and deconstructive interference, and I do not understand them through the text. I would benefit from some for visual examples in the class to distinguish the two apart."

"Nothing too confusing."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Are we going to listen to speakers in class?" (Oh, yes.)

"So are we doing a lab with sound soon?" (No, but you will have two labs with interfering light waves.)

"If two waves are coherent, do they create constructive interference, if they travel the same distance?" (Yes, provided that they also start in phase from their sources.)

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