Waves and Oscillations

Oscillations are fundamental to all waves. We can study the inherent harmony present in all entities of the Universe using the concept of harmonic (periodic) oscillations. Guitar strings, pendulums, quartz crystals and pistons are few of the myriad harmonic oscillators that we encounter in daily life.

In the apparently chaotic natural world there are systematic waving and oscillating patterns. Studying these patterns in nature is like probing the method in her madness. Jean Fourier, the French mathematician was the foremost to reveal this method when he theorized that any complex periodic phenomenon could be understood as a combination of several simple harmonic components. Let us see

A wave is characterised by several parameters, primary among them being amplitude, frequency and phase. Amplitude of a wave means the size of the disturbance, i.e., the strength of its oscillations. Increasing the amplitude of sound wave makes it louder and light wave brighter. Frequency means the number of oscillations in one second and phase relates to the state of vibration.

The propagation of electromagnetic waves can be understood in terms of charge oscillations. Whenever electric charge oscillates, a disturbance characterized by the existence of alternating electric and magnetic fields propagates outward from it that we know as an electromagnetic wave. In electromagnetic waves the oscillating electric and magnetic fields carry energy and information. As electromagnetic waves can travel long distances without much damping they are widely used for communication. The carrier electromagnetic waves carry the sound and picture signals from the place of transmission to the place of reception without anything material getting transmitted.

Resonance

Physics of waves and oscillations enables us to understand a large variety of natural phenomena. One very interesting phenomenon is resonance. In forced oscillations when the frequency of driving force equals the natural frequency of the vibrator the amplitude of vibration becomes maximum and the vibrating system is said to be in resonance.

Resonance may occur in any structure as all structures have one or more natural frequencies and the resulting oscillations may even rupture the structure. In 1940, the newly constructed Tacoma Narrows Bridge at Washington was collapsed due to mild wind that set up the bridge in resonant vibrations. Thus, the soldiers are asked to break in their steps while crossing a bridge as their rhythmic march can resonate with one of the natural frequencies of bridge. Aircraft designers ensure that none of the natural frequencies at which a wing can oscillate matches the frequency of the engines in flight.