## Wave Experiment Lesson

28 Feb

Welcome!

This page will provide you with everything you need to know about completing your upcoming in-class experiment on wave mechanics. Begin with the subject background information and take some time to familiarize yourself with the key concepts and terms related to waves. After you have the basics down, thoroughly review the experiment procedure so you know how to set up this experiment and properly record observations before we get started. You might not have time to finish the experiment in class if you have to learn what you’re doing when you should be getting started!

INTRODUCTION TO WAVES

• There are 3 primary types of waves:
1. Surface Wave: A vibration along the interface between two media. For instance, the surface of a pool of water is an interface between water and air.
2. Transverse Wave: The medium oscillates perpendicular to the wave’s direction of travel. If a transverse wave travels horizontally, then its medium is displaced vertically.  Watch it in slow motion:
3. Compression (Longitudinal) Wave: The medium is squeezed and stretched parallel to the direction of the wave’s travel as it passes over.   Sound is a compression wave, it can travel through a solid, liquid, or gas. Where the medium is squeezed you have Compression, where it is stretched you have Rarefaction.

Which of these is a transverse wave?

PROPERTIES OF A WAVE:

– We describe all types of waves using the same specific measurable qualities.

– The velocity of a wave is described simply by its speed and direction, just like an ordinary object, and depends on the nature of the medium. For example, sound waves travel faster in water than air.Velocity (v) = Distance (x) / Period (t)
– We also describe a wave’s Frequency (f), which is measured in oscillations over time (ex. 4 cycles per second) – we call this Hertz (Hz).  A sound’s pitch is its frequency. The frequency of a Concert A is 440 Hz.
– When the wave reaches the end of the medium, it still has energy and will tend to continue propagating. Whether or not it inverts depends on whether the end of the medium is held fixed, or is elastic.
• Is this a mechanical wave? Click the image to loop it and Click here for the explanation…
• One last example:

What type of wave is traveling through the guitar strings? What type of wave is traveling between the strings and your ears?

The Experiment

You will work in groups of at least 3, two people holding ends of the slinky and one person holding a stop watch. Familiarize yourself with this procedure now, so you’ll know what you’re doing when class begins, and bring up any questions you have early on: Slinky Experiment

*This entry was created for an education course in instructional technology. This Write-Up explains my thought process in designing this unit lesson plan.

## Physics – Let’s do it

7 Feb

For starters, I must acknowledge that this blog addresses a rather broad subject. Physics attempts to describe observable events on vastly different scales, such as a car on the road, a proton in a magnetic field, and even the motion of the Milky Way galaxy as it careens haphazardly through the Universe. Exciting, no?

Unfortunately, we presently need 3 different versions of Physics to work in each of these systems. The classical scale, being the things we most commonly perceive, ranging from objects as small as the human hair up to something the size of the entire Earth. This is the oldest language of Physics, by human standards, which early scientists like Isaac Newton were able to define through experimentation.

Now we go down to a much smaller scale – Quantum Mechanics, or Particle Physics, which deals with tiny subatomic particles. Some of these particles are familiar: Protons, Neutrons, and Electrons, but the world of particles is, pardon the expression, Big. Sometimes these particles interact with electromagnetic radiation in the form of photons, and sometimes a rather bizarre type of Force causes particles such as muons, pions, or tauons to burst out of larger particles during a complex interaction. The Quantum scale is its own little world, really.

Last, we have the seriously big scale: Cosmology. Consider the distance between the Earth and the Sun, so vast that it would take 8 minutes to make the trip at lightspeed. This is a brief jot on the Cosmological scale, however, where a more common way to measure distance is in terms of how many thousands of years it would take light to travel through space. For example, modern observations of deep space first produced by Edwin Hubble (as in the Hubble telescope) suggest that the Universe itself is expanding constantly. How much space do you have to look at to really notice it’s expanding? You’d have to stand back quite a ways. The Hubble expansion constant measures the expansion of the Universe in terms of Megaparsecs – where one Megaparsec is about 3,262,000 Light Years. Pretty damn big.

So, Physics has a bit of problem in this regard. None of these three branches of Physics is currently capable of describing either of the other two. Will we, one day, have an understanding of the Universe that allows us to work on any scale using just one language of Physics? A pipe dream, perhaps, but in the meantime, just keep doing Physics!

7 Feb