Today 1/16 Waves Interference of Waves HW: 1/16 HW Handout “Superposition”

Due Wed, 1/22 (beginning of class) Read: Ch 16.1,2,5 Ch 17.1,2 Suggest: Problems 16-1,2,3,4,5,8 Note: This “lecture” is mostly animations and is

more than 80 slides long! Beware the print button!

Things to think about:

How would you define a “wavelength?”

How would you define a “frequency?”

How would you define a “wave velocity?”

What happens when two waves run into each other?

Consider a traveling wave: sound, light, football stadium, water...

How does the direction of the wave’s motion compare to the direction of the individual particle’s motion?

How does the direction of the wave’s motion compare to the direction of the individual particle’s motion?

Wave moves right while particles move up and down.Called a “transverse wave”Examples are light, water, and football stadium, sound is a “longitudinal wave.”

Wavelength () = ? = 8 units

Wave Velocity (v) = ? Direction is to the right, v = x/t

v = /Tx is and t is T, the time for a particle to go through one complete oscillation, as in SHM.

Frequency, f = 1/T also as in SHM.v = f

What happens when two waves collide?

waves just meeting

?

Superposition!!!

Green wave says move up but blue wave says move down so...Particle does not move!!

??

Superposition means “superimpose” all effects at a chosen location then add them up (as vectors) to get the “net” effect at that location.

Only overlap here.the two waves are right on top of one another.

Now let’s put this in motion.

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

Destructive interference Constructive interference

This is a “standing wave” and is a “superposition” of two traveling waves. These two waves “interfere” with each other causing locations of “constructive” and “destructive “ interference.

Destructive interference Constructive interference

Note that the locations of “constructive” and “destructive “ interference alternate. These locations are called “nodes” (destructive) and “anti-nodes” (constructive).

Your first Homework...