this is a good jdk simulation of the Cathode Ray Oscilloscope (CRO).

will there be an Ejs version soon? i don't think anyone has made one in Ejs yet.
for your consideration  ;D



btw i found some java applet here
http://www.phys.hawaii.edu/~teb/java/ntnujava/oscilloscope/oscilloscope.html by hwang@phy03.phy.ntnu.edu.tw
http://www.ece.ncsu.edu/virtuallab/JAVA/applets/osc.html by daniel hoag and erwin d'souza copyirght NC state university
http://www.csupomona.edu/~pbsiegel/gsix/oscilloscope.htm by Peter Siegel California State Polytechnic University

the learning objective is
Determine the frequency of sound using a calibrated C.R.O.

Determination of frequency of sound using a calibrated C.R.O.

Sound are longitudinal waves of compressions and rarefactions through a physical medium, for example air.

The frequency of the sound waves from a given source could be determined using a calibrated cathode-ray oscilloscope (C.R.O.) as follows:

- the source of sound e.g. a loud speaker is placed a short distance from a microphone connected to a calibrated C.R.O. as shown.
- The time base of the C.R.O. is adjusted until a stationary trace is obtained.
- The period of the sound wave is given by the product of the length of one wave cycle and the time base setting.
- The frequency of the wave is the reciprocal of the period.