The original double slit experiment 7:39 min video presented by Derek Muller of Veritasium in which he takes a cardboard box to the beach and demonstrates the wave nature of light to passers by. (Jnr Science, Phys 2.3, 3.3)
Interference with plastic wave model
This practical activity, using acetate sheets of waves, on cocktails sticks, from Practical Physics.org is a great way to get students thinking about why nodal and antinodal lines form where they do. A word document, with waves of two different wavelengths can be printed on acetate sheets from here. And worksheets are here.
Sound interference illustrated with two speakers connected to a single signal generator
Sound interference with a ‘sound trombone’, from the IoP’s Advancing Physics course, episode on interference.
Shows reflection with inversion for transverse and reflection for longitudinal pulses.
Diffraction and Interference of Water Waves
Photos of water waves at an Eastbourne beach showing diffraction and interference effects.
Wave properties such as interference are demonstrated with a tabletop wave tank, displayed using an overhead projector.