Wave Energy

harmonics will be multiples of the fundamental frequency. The fundamental frequency is seen in figure 105:

Figure 105.

Taking this to another level, you can see that hitting two adjacent keys on a piano is an unpleasant experience because there will be the superposition of two waves of similar but not the same frequencies. There will be two waves that go in and out of phase. This will lead to a “beat” heard when the waves are the loudest. At any point in time, the wave amplitude x will be equal to the total amplitude multiplied by the cosine of the multiplication of 2 times pi times the frequency times the time. The amplitude at any point in time will be the amplitude of one wave added to the amplitude of another. The beat frequency will be the average of the frequencies of two separate waves. Piano tuners will listen until the beat goes away to zero frequency.

WAVE ENERGY

All waves will have energy. Think just of earthquakes, which have energy that can shake entire villages and cities until they are destroyed. Ultrasounds have energy that treats muscle strains and lasers have energy that can destroy tissue. The energy of a wave is related to its amplitude. Waves are displacements that are resisted by a restoring force. The larger the displacement, the larger the force needed to create the wave. A waves energy is directly proportional to the square of its amplitude so that work is equal to a force constant multiplied by the displacement squared.

Another thing that affects the energy of a wave is the time. More energy is applied over time with waves being concentrated or spread out. This leads to the definition of the intensity of a wave, identified by the letter I, which is power per unit area. The SI unit for intensity is watts per meter squared. Other units commonly used include the decibel, which is 10-3 Watts per meter squared.