Waves Demos

Equipment: (These are kept 178 DA.)

Demo 1: Transverse waves

Orient the wave device so that the ends of the rods face the students. Move one of the rods on one end up and down. Note that the wave appears to move along, but the rod which makes up the wave only moves up and down. This helps to explain the equation for a transverse wave: y=A*cos(omega*t-kx)=A*cos(2pi(t/T-x/lambda))=A*cos(2pi*(v*t-x)/lambda) A rope with a marked point can also be used to demonstrate the same principle. Tie one end of the rope to a fixture at one side of the lecture hall, and shake the other end up and down to make traveling waves. Mark a point on the rope so that the student can see that each point is only moving up and down even though the wave appears to move horizontally.

Demo 2: Longitudinal waves

Get a volunteer to hold one end of the slinky, and stretch is gently in the from of the lecture hall. Move your end back and forth longitudinally and produce longitudinal waves. Say that this is like sound waves in air.