This work would not have been possible without the expert simulations created by The PhET Team, particularly its superb software developers Sam Reid, Chris Malley, John Blanco, Mike Dubson, and Jonathan Olson. PhET is supported by the National Science Foundation, the William and Flora Hewlett Foundation, The Excellence Research Center of Science and Mathematics Education (ERCSME) at King Saud University, JILA and the University of Colorado. ERCSME is funded by the Ministry of Higher Education in Riyadh, Saudi Arabia, ERCSME is grateful for the Ministry of Higher Education and King Saud University for their continuous support.