Light And Sound Analysis

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Physics: Analogy of Light and Sound

Light and sound share many common aspects. Today, we will study some of notable similarities and differences between the two.

We can perceive both light and sound. We see through eyes and hear through ears. Both light and sound are waves. Light is an electromagnetic wave whereas sound is a mechanical wave. Light is created by interaction of electric and magnetic field. It does not require any medium for propagation, so it can propagate in free space. On the other hand, sound wave requires physical medium, such as air, in order to sustain itself. For example, vibration of vocal chord creates cycles of compression and decompression of air molecules, and our ear detects this subtle movement of the air molecules.
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With sound, we can distinguish different pitches, such as Do, Re, Mi, Fa, and so on. Well, what physical aspect determines the color and pitch? It is the frequency of the waves that gives us different perception. We all know that higher frequency sound waves have higher pitch. The faster the oscillation, the higher pitch sound it gives. Our ears can only detect a certain range of the frequencies, called the audible spectrum or audio frequency. Although the audible range differs from person to person, it is generally from 20 to 20,000 oscillations per second. Sound having frequency greater than the upper limit of the audible spectrum is called ultrasound. Prenatal ultrasound uses this ultrasound wave to see through the abdomen and shows us images of a baby in the womb. Sound having frequency lower than the audio spectrum is called …show more content…
Light with the lowest visible frequency is perceived as red color whereas light with the highest visible frequency is perceived as violet. Other colors lie in between the two in the order of rainbow, for example, red, orange, yellow, green, blue, indigo, and violet. When Newton first discovered the visible spectrum and divided corresponding colors, he chose 7 different colors by analogy to the number of music notes. In fact, the visible spectrum of light is only a very small portion of the entire electromagnetic wave spectrum. Light with frequency slightly lower than the red color frequency is called infrared, whereas light with frequency slightly higher than the violet color frequency is called ultraviolet. Unlike sound, however, light spectrum consists of numerous other notable bands, such as radio frequency, microwave frequency, x-ray, and gamma ray. It is amazing that all these describe exactly the same entity, which is electromagnetic wave, with difference in frequency only, and yet exhibit so much difference in their physical characteristics.

Different species of organisms adapt to hearing and seeing different spectra of sound and electromagnetic waves for their survival. For example, dolphins and bats use ultrasound for navigating their ways in pitch-black environment. In general, wave at high frequency exhibits ray-like properties, which make it more suitable than lower frequency wave for detecting objects

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