Using horizontal sensitivity to evaluate time period. By measuring the period of the wave on the horizontal axis of the oscilloscope screen and reciprocating that time value (in seconds), you can determine the frequency in Hertz.
The oscilloscope is used to measure the characteristics of a voltage. The time period of a sinusoidal alternating voltage is here studied exclusively, without worrying about the Vpeak.
Oscilloscope: type of electronic test instrument that graphically displays varying signal voltages.