Unit 9

Today's new unit is about waves. We learned that waves are just a transfer of energy. Waves and vibration can easily be confused. Waves are up and down motion with direction (in class defined as a wiggle in time and space), vibration is just up and down motion. A medium is a substance by which another substance is carried or transferred. Light and sound are good examples of waves. Light comes from the sun and travels at the speed of light. Light is special because it doesn't need a medium to transfer through. Sound, like radio waves, travel through air (the medium) in longitudinal waves.
There are two types of waves we learned about. Transverse waves, in which energy moves perpendicular to wave motion, and longitudinal waves, in which energy moves parallel to wave motion.

A wave length is measured from two corresponding points, like crest to crest and trough to trough. The crest is the top of the lump and the trough is the low scoop in the diagram. Wave lengths can also be represented by the Greek sign lambda. Wave lengths travel the fastest in the most dense medium. An amplitude is measured by the midpoint of the wave to a crest, as shown in diagram.
We also learned yet another new equation:
v = ƒλ 
V = velocity, ƒ = frequency, as measured in hertz, and λ  = wave length, what I just explained. Frequency is defined as the number of oscillations (cycles) per second.
Credit to: http://img.tfd.com/cde/WAVELEN.GIF

My candid shot of Ari & the spring pen lab is a reminder of what we learned today! In this lab, we tried to knock down certain whiteboard pens by only using a very large slinky and our knowledge of waves. I'll give you a hint: we succeeded using constructive and destructive interference!