Oscilloscopes have parallel metal plates inside them to deflect the electron beam. these plates are called the deflecting plates. typically, they are squares 3.00cm on a side and separated by 5.00mm , with very thin air in between. what is the capacitance of these deflecting plates and hence of the oscilloscope. (this capacitance can sometimes have an effect on the circuit you are trying to study and must be taken into consideration in your calculations.)