Tuning forks are used to tune instruments because they resonate at specific frequencies determined by their shape, size and material. Most will have a letter printed onto them which corresponds to the sound of the note they create when rung.
To make the fork ring, hold firmly by the handle end (the bottom of the 'Y') and tap the side of one of the two prongs onto a solid surface (eg, a desk edge) Without touching the vibrating prongs, stand the fork upright on its handle on a table. It should ring loud enough to hear clearly. The desk acts as a sounding board, amplifying the note.
Using an oscilloscope and microphone, the sound the tuning fork makes can be seen as a wave on the oscilloscope screen. Different forks can be used to show the differences in wave form due to the different frequencies being produced.
Tuning forks can be purchased through lab suppliers or though music shops singly or in sets
Tuning forks are also available mounted on resonator boxes which amplify the sound greatly allowing the class to hear the note produced.