What would you think of an experiment where you drop your mobile phone into a tank of salty water to see if it still rings?
CPAS Visiting Fellow and University of Canberra Physics Professor John Rayner devised this student-centred experiment, undertaken by two year 10 students, that does just that except that the phone is in a waterproof container.
The phone still stops ringing when it reaches a critical depth called the “skin depth” due to the absorption of the wireless signals to the phone by the salt water. The skin depth depends on the frequency of the wireless signal to the phone and the electrical resistance of the water.
The students investigated, successfully, the relationship between resistance and skin depth and confirmed that the investigation was interesting, doable and valuable to high school science students.
The effect has important applications relating to wireless communications with submerged submarines.
Want to do this experiment in your high school science classroom or physics outreach event? Read the whole paper.