Question

Two phenomena for waves you have seen this week are interference, specifically spatial, and resonance.

For each phenomenon, describe briefly what is happening and why, then considering that each one can be good or bad depending on the situation, see if you can give two cases for each - 2 where good, 2 where not good.

Please no handwritten or picture responses - only typed replies.

Answer 1

Interference takes place two waves of different parameters superimposes each other. This interference can be of destructive type in which the combined amplitude will become 0, or it can be of constructive type where the combined amplitude is maximum, and it will be larger than the amplitude of waves.

For eg. Consider two sound waves, each sound wave have different pressure variations, ie. they consists of crests and troughs, Now, imagine if one crust and one troughs combines, in that case the variation will be cancelled and the amplitude of the wave will become zero. And if two crests or two troughs are combined, the amplitude of the wave increases (doubles).

Resonance is a phenomena which happens in presence of driving force, in this when the frequency of driving force equals the oscillation of the system, then the amplitude of oscillation of the system increases, ie. the Energy in the oscillation of the system increases.

Interference eg.

Good :Multiple colors on a thin oil film on the road, Noise cancellation of Head phones.

Bad : Abberations caused in image due to Interferance, and radio channel disturbances

Resonance eg.

Good: Pushing a person in a swing(having Fun) , Music instruments use resonance to amplify sounds

Bad: Building breaks down completle during Earthquake, due to matching of natural frequency of the building with the force frequency of earthquake, Collasping of bridges due to its oscillation resonating with the flowing wind.