The mechanical and electromagnetic wave
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Published: Mon, 5 Dec 2016
A wave is a moving disturbance that transports energy from one place to another without transporting matter. Any wave is characterized as sort of “disturbance” that travels away form its sources. There are two examples of waves, mechanical waves and electromagnetic waves. Mechanical waves travelling through a material medium, such as water waves, sound waves and the seismic waves caused by earthquakes. Particles in the medium are disturbed from their equilibrium positions as the wave passes, returning to their equilibrium positions after the wave passed. Electromagnetic wave such as radio waves and light waves which has the disturbance consists of oscillating electromagnetic fields. Two of our five human senses are wave detectors: the ear is sensitive to the tiny fluctuations in air pressure caused by compression waves in air, which is sound whereas the eye is sensitive to electromagnetic waves in a certain frequency length that is light. (Richardson 2004).
The examples of mechanical wave and electromagnetic wave
One of the examples of mechanical wave is sound wave.How does a sound wave be created? First, the disturbance from one location to another which carried by any medium. By far, the most familiar case is sound in a gas such as air. Second, there is a unique source of the wave. The vibrating object which creates the disturbance could be the string of a violin or guitar, vocal chords of a person, tuning fork, etc. Third way is particle-to-particle-interaction. If the sound wave is moving through the air, it will pull or push its nearest neighbors, causing a disturbance of its nearest neighbors. (National Science Digital Library Science, 2003).
Besides, seismic wave is an example of mechanical wave. Seismic wave is a result of an earthquake, explosion or some others process that give out force. There are several different kinds of seismic waves, and they all move in different ways. There are two main types of seismic waves; they are body wavesandsurface waves. Body waves propagate into the body of the Earth. On the other hand, surface waves can only move along the surface of the Earth. Those are similar to water waves on the surface of a lake. Earthquakes radiate seismic energy as both body and surface waves. (Michele, n.d.). Seismic waves carry energy released by an earthquake to other parts of the Earth, sometimes with devastating results.
There are lot types of electromagnetic waves. The one of the examples, radio waves which is used to carry conventional radio and television signals as well as signals for some cell phones and pagers. In addition, microwaves, X-Rays and gamma rays are also types of the electromagnetic spectrum. Microwaves in ovens carry energy from their source to the food. (Richardson 2004). Gamma rays are not only produced in nuclear power plants and the Sun, but also reach the Earth from the sources outside our solar system. The radiation people are able to detect by eyes falls into the rather narrow frequency range. This radiation is called visible light. Proceeding to frequencies above the range of visible light is ultraviolet light.
The tragedy caused by wave
The earthquake struck in Hanshin is caused by seismic waves which was the worse to hit Japan since the great Kanto earthquake of 1923. The 7.2-magnitude GreatHanshinEarthquake of 1995 hit the Kobe area at 5:46 a.m. on Tuesday, January 17, leaving in its wake more than 5200 deaths, 30,000 injured, 300,000 homeless, and 110,000 buildings damaged. (Fukushima 1995). How did the earthquake cause great devastation at locations many kilometers away?
Seismic waves travel away from the focus of an earthquake both through the Earth (body waves) and along the Earth’s crust (surface waves), transporting vibrations and energy. However, the material through which the waves travel is not transported. Most earthquake damage is caused by seismic waves rather than caused by fault movement. In the Hanshin earthquake, damage to the buildings was caused by seismic waves at distances over 100km from the epicenter, but the motion of the vibrating particles in the ground never moved than about 1.5m. (Giambattista 2004)
Optical phenomena (Atmospheric optics)
The unique wave properties of the atmosphere cause a wide range of spectacular optical phenomena. One common example would be therainbow, when light from the sun is reflected and refracted by water droplets. Some, such as thegreen ray and Fata Morgana are so rare they are sometimes thought to be mythological.(John 2006)
Why is the sky blue and not violet?
The Rayleigh scattering of light by molecules in the atmosphere gets stronger as the wavelength decreases. We have claimed that this scattered of light gives the sky its blue light, so why isn’t the sky violet instead? Two factors combine to make the sky blue instead of violet. First, the Sun emits more strongly in the blue than in the violet range (according to Fig.1). Second, people’s eyes are more sensitive to blue light to violet light. Hence, even though violet light scattered more strongly than blue light, people still perceive the sky is blue. (Nicholas, n.d.)
- Hotter objects emit most of their radiation at shorterwavelengths; hence they will appear to bebluer.
- Cooler objects emit most of their radiation atlonger wavelengths; hence they will appear to beredder.
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