The nature of a wave was discussed in Lesson 1 of this unit. In that lesson, it was mentioned that a wave is created in a slinky by the periodic and repeating vibration of the first coil of the slinky. This vibration creates a disturbance which moves through the slinky and transports energy from the first coil to the last coil. The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium.
Frequency is a part of our common, everyday language.
In mathematical terms, the frequency is the number of complete vibrational cycles of a medium per a given amount of time. If a coil of slinky makes 2 vibrational cycles in one second, then the frequency is 2 Hz. If a coil of slinky makes 3 vibrational cycles in one second, then the frequency is 3 Hz. The quantity frequency is often confused with the quantity period. Period refers to the time which it takes to do something.