Wave Motion

Wikipedia has a good definition of a transverse wave in a fairly easy to understand way.

http://en.wikipedia.org/wiki/Transverse_wave

Electromagnetic waves are pretty much what the word implies. The wave has two components oscillating at right angles to each other (one magnetic and one electric) along the direction of propagation. Imagine a 3-axis grid. The X axis could be thought of as the magnetic wave's orientation. The Y axis would be the electrical wave's orientation (90 degrees from the X axis). The Z axis represents the direction that the wave is traveling. The frequency of the electromagnetic wave defines its type. At the lower end of the scale are radio waves, which can be in the Hz range for some very low frequency RF. Yes, that is a below audio sound, but it is a different type of wave as you will see. Radio waves run up to about the GHz range in frequency. Next is the microwave region that extends upward of 1 GHz. Then you have infrared, visible, and ultraviolet light. Finally, you have the highly energetic X-rays and Gamma Rays at the extreme end of the spectrum.

Longitudinal waves are the opposite of transverse waves. Transverse waves, if you remember now from Wikipedia, oscillate at a right angle to the direction they propagate. Longitudinal waves oscillate in the same direction as they propagate. Sound is an excellent example. If you ever watched a speaker cone move at very low frequency you realize that it is simply a piston that moves in and out. As the piston strokes outward it compresses air in its path. The cone then reverses and rarifies the air as it withdraws back into the speaker basket. As this happens, sound projects outward from the speaker at about 340 m/s. If you take a snapshot from the side of this and could see the air molecules in front of the speaker you would see areas of high density followed by areas of low density air. This is called a longitudinal wave. The oscillation is along the axis of propagation (long ways).

The same thing happens when sound propagates through water, steel, or other mediums. The material in the medium compresses and decompresses in density as the sound wave travels through it.

I hope that sheds some light (no pun intended) on the subject.

That's alot of information but it did help a little bit.

**no pun taken lol**

Hi Physgrl80: you asked about:

"First off Do electromagnetic waves include light waves, heat waves, microwaves, etc.?"

Electromagnetic waves (emw's) include from light to radio waves and microwaves are radio waves. Heat waves are in infra-red part of the light spectrum. Further, emw's have two components that move together at the speed of light. As the name implies, the two components are magnetic and electric and they are polarized at 90 degrees to each other. Read more about them on this Wikipedia page.

"Transverse wave- particles that move at 90 degrees to the direction of the wave. *ex. spring* Is this right?"

Basically, yes. Waves in water are also essentially transverse and so are emw's. Waves in a spring may or may not be transverse, depending on how it is exited.

"Longitudinal wave- I really don't understand what the teacher was talking about during this lengthy and complicated definition. All I've gotten from it was that sound waves are only longitudinally waves."

Longitudinal waves have particles or molecules that move backwards and forward in the same direction as the wave motion. It can be thought as a pressure increase that propagates through a medium, like sound or earthquake waves. You can read more on both types in this Wiki article.

"I'm also not understanding the concept of a simple harmonic motion."

It is just like a sine or cosine wave or pendulum that swings. This Wiki article says: "Simple harmonic motion is the motion of a simple harmonic oscillator, a motion that is neither driven nor damped. The motion is periodic, as it repeats itself at standard intervals in a specific manner - described as being sinusoidal, with constant amplitude."

Hope it helps! (I prefer to say just a little and point you to where you can read it in depth.)

Regards, Jorrie

Thank you soo much. I appreciate your help!!

Schaum's Outlines saved me from a crappy physics teacher - I highly recommend them.

Using special cameras we have captured a Royal Wave and need some help to put it in one of your catagories. See below.

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Wonder if the "old girl" needs a surf board.

Hey PetroPower, I would be very careful about the flagrant display of a sense of humour on this site. Some of the lads tend to get a tad hyped! You obviously did not catch physgrl80's last posting, the lynch mob were after me in a big way.

Sorry physgrl80, couldn't resist that one! Suffice to say the earlier threads should have given you more that enough leads for your work. Good luck!

Answers 1 and 2 are excellent.

When I went through University Engineering it was all laid out pretty straight forward.

However, I am starting to think some college profs are now teaching in some vague "discover it yourself by group discussion techniques" and "if you really think about it you will reason the answer". My daughter in her undergrad program suffered through this BS way, then discovered there is a wealth of knowledge waiting to be read in books, and that a lot of the physics have been well laid out for many years. I got the impression her prof really didn't know, and was determined to fail as many as he could.

My daughter just graduated with her MSc at UBC, so do not feel you are alone or necessarily incompetent.

I remember my old day where I did interrupt a PhD in Physics with simple questions as there are: what about the weight of the spring? He had no direct answer but he appreciated my question, he did his paper on a different domain (I hope so). I've had teachers who's reaction was to give me a 0 on the next exams.

The problem is that teachers are incapable to do normal work so they go teaching (and the head of the school if happy that someone is there to entertain the kids) or they are aiming for other functions. The real people that should be teaching are those who gain a double or more in the industry.

As they say - "Those that can - do, Those that can't Teach"

Read Napoleon flounce at the bottom of my thread, and draw your own conclusions. that is, if you can.

Wangito.

and those who can't teach, teach teachers to teach.

I guess you are referring to YOUR teachers, You must be right, as We can see the results. And maybe it is not entirely their fault, as you seem to be stupid by nature.

I have dared insulting you, (on purpose of course), as you have dared insulting a huge group of people to whom you owe your little knowledge. (if any).

Don't forget: WHEN GENERALIZING, YOU ARE INCLUDED.

Wangito.

Napoleon's quote from Wateloo, if I remeber correctly. How about this one:"Stupidity is curable, ignorance is not"(or is it the other way round)

Exam question I had a couple of years past:

Qualify the following statement:"Generally speaking, generalisations are generally false?" True or False.

Qualify.. Qualify.. like H*LL, that question didn't even make the starting grid!!

Well said, Wangito. Although I'm doing both electronic and mechanical engineering now, I taught physics, electronics, etc. for 32 years, including a couple of years in Santiago (Escuela Electrotecnica) back in the 60's. Unfortunately, by the 90's, I found that the fraction of students who were genuinely interested got so low that I took early retirement at 55.

Also unfortunately, there have always been some of those who cant, so they teach (there are bad apples in every large box), and as schools are forced to teach to a particular set of tests, rather than teaching a love of learning, I suspect that the proportion of the bad apples has grown.

That is exactly what I try to explain: the one's that can get frustrated by the system. Those who like the system are usually not the best.

I've had excellent teachers, that how I ended up in Pure Mechanics, and I've seen others burn down and crack in the system.

I've also seen students who didn't knew the difference between Joule and Watt and they also got their master degree.

The same thing happens in language classes: you lean exactly how to use verbs and other grammatical stuff, but learning to listen to someone is a bridge to far. Who used the written skills of foreign languages in their professional life? 10% perhaps, but everyone could use simple verbal skills.

I've had good teachers and of course bad ones, but my major gripe was with so many of the chosen required textbooks, along with the lack of integration between related subjects such as physics and calculus. I always found older calculus textbooks clearer and more "understandable" than the ones I was using. My biggest peeve was when calculus textbooks had problems based on techniques that were not even covered anywhere in the book, let alone that chapter. One textbook I had was used for three semesters of calculus, and we only ended up covering about 2/3 of the chapters, so naturally it was light on the examples and explanations. I well remember the many hours wasted trying to locate similar problems that were explained in other books. Meanwhile, calculus is so useful and powerful yet seems to be taught as too much of an abstraction, far removed from everyday applications. Had I not been a physics major, I doubt I woulld have gotten much out of it at all.

I agree completely. There is this idiotic sterile and exacting approach to teaching calculus that makes it incomprehensible till you develop a working knowledge of it through experience.

There's a great story about Neils Bohr's lectures that's analogous. Neils Bohr was obsessed with language and meaning. He felt people were not careful enough when they spoke and often this led to misunderstanding. He was determined to be extremely precise in what he said, particularly in his lectures, to avoid confusion. So when he lectured, he would give incredibly precise and detailed explanations that stretched on and on so as to eliminate the possibility of misunderstanding.

It was a noble attempt, but there was only one problem, no one understood what the hell he was saying. In his attempt to be precise he often used rare words which most didn't know the meaning to. His explanations stretched out so long that people forgot the original topic. Towards the end of the lectures, people were so worn out they were no longer listening. He was commonly regarded as a terrible lecturer.

A classic case of the cure killing the patient. This is exactly what is happening with calculus. It is taught with such an eye to being precise that all the meaning is lost. What's worse is it is the natural disposition of the teacher to blame the students lack of interest than the teaching methods which are making the subject unlearnable.

It's not like my teacher doesnt try, and just tells us to stare at the bored and learn. It's the lectures that kill me. I learn by lecture and visual i've come to learn. One without the other just makes understanding things a bit complicated. Dont get me wrong if i have to learn by lecture or by visual i do try to get everything i possibly can out of it! Sometimes i do need a little extra help though.

Thanks very much!

Comment on understanding simple harmonic motion.

Whilst it is implict when you understand the derivation, even the Wiki article does not show it as a point rotating on a circle, but viewed a 90 degress to the circle axis. When one of my lecturers explained it in this manner and drew in on the blackboard (many years ago I note), it all became clear to me.
Hope this helps.
KenS