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| The red and green waves sum together to produce the red wave..Image author Wolfgang Christian and Francisco Esquembre CC BY SA4.0 International via Wikimedia Commons |
The
red wave is the sum of the green sine wave travelling right and the
blue sine wave travelling left. When the peaks of the red and blue waves
are coincident and they add, the result is constructive interference
and when peaks coincides with troughs, they subtract, resulting in
destructive interference. The waves can be sound, light, radio waves,
waves in the sea, ripples in a pond, gravity etc. Wave interference is
responsible for the phenomenon of iridescence (e.g. colours on spilled
oil or petrol on a wet road), beat frequencies with sound waves (e.g.
two tuning forks giving a tremolo effect and periodic rise and fall in
sound level) and contouring of coasts when sea waves combine. Coastal
features called tombolos where an island joins to the mainland by a sand
bridge (e.g. Howth Head or Palm Beach in Australia, used as the film
location for the fictitious Summer Bay in Home and Away) are caused by
refraction (a type of interference of sea waves).