The LIGHT and SOUND show – Audible Sound as Invisible Light
As the day dawns, we have the beautiful rays of sunlight caressing us and the melodious voice of the chirping birds calling us to wake up.
As the day draws to an end, we have the galaxy of stars glittering in the dark sky and it is time for the moon to makeup our mood for a candle light dinner.
The romance of life is in the little light in the canvas of darkness that engulfs the evening sky. It is time for the nocturnal animals and birds to wake up and make us realize that there is light and sound in the dusk of life. There are feeble sounds which we don’t hear in the daytime we can hear it in the silence of night and there are faint lights which we cannot see in the daytime we can see it in the full darkness of night.
Darkness is nothing but merely an absence of light.
In other words when light departs darkness enters. It is this magical paradox that is musically played through this light and sound show in the theater of life.
Is there a similarity between light and sound?
The answer for many things in life lies in the art of asking the right question, never easy to ask a simple question as it appears silly and once the question is rightly framed, the mind starts to work meaningfully to get the right answer.
The answer for the aforementioned question encompasses duality i.e. both a ‘Yes’ and a ‘No’. It is this very intriguing interplay that makes the display quite interesting. Herein lies the most fascinating facet of this light and sound show we keep seeing and hearing in everyday of our life, and dazzling display is all around us.
Soaked and served with little bit of everything…
The light is a wave.
The sound is also a wave.
The similarity ends there.
The difference is in the type of waves. Light is an electromagnetic wave. It propagates in the empty space by modifying the electrical and magnetic fields. The waves are of different types. These different types of waves have different purpose to serve. Light is a transverse wave. Sound is a longitudinal wave. The light can travel in vacuüm. The sound cannot travel in vacuüm. The sound needs a medium. The medium could be in any form like gas to liquid to solid state.
The dissimilarities end here.
The light is a form of energy.
The sound is also a form of energy.
The speed of light and speed of sound is different. One striking example in nature we see is the striking of lightning and the hearing of the thunder in the sky. It is caused by an explosive rupture of accumulated electrostatic charges as electricity. The light travels to earth as light waves and the thunder travels to earth as sound waves. In reality thunder is the sound caused by lightning. Hence thunder is not possible without lightning. But many times we see the lightning but don’t hear the sound of thunder. These are typically called a silent or heat lightning. It is possible as the distance of the thunder was far off to reach us. Not just different but the difference is humongous.
What are light and sound comprise of?
A ray of light is called as photon. Light is a fundamental particle and it is also a wave. Sound on the other hand is a wave but not a particle. The speed of sound varies whereas the speed of light is constant. For instance, the speed of sound is 343 meters per second through air. The speed of light is 1,86,282 miles per second. This is around a million times faster the speed of sound in air. The speed of sound varies from medium to medium but as the speed of light is independent of medium it remains constant.
Light and sound can be reflected, refracted, interfered and diffracted.
These are different response to the waves when they meet different mediums in the journey. The effect and impact is equally different. The property remains but our perspective of light changes as it enlightens us.
Sound needs a particle to travel and radio waves are also particles and hence sound travels through the light waves. All light waves are not visible and the most intriguing aspect of the connection between the sound and light is that the invisible part of light spectrum known as the radio waves makes the silence of sound audible. It is the radio waves that transmit the sounds to far off place. The sound we hear in transistors or radios to televisions. Sound wave travels at 766 miles per hour as against radio waves at 1,86,282 miles per second. Comparing the distance these can travel in the same window of time, sound waves will merely cover one end of a stadium to another end while the radio waves would have completed it tour of the planet…it immediately puts things into proper perspective.
It was way back in 16th Century; Leonardo Da Vinci discovered sound travels in waves. Martin Mersenne was the first person to measure sound in air. In 17th Century, Isaac Newton discovered that prism can show the seven colors of light. William Herschel discovered the Infrared. Wilhelm Ritter discovered the Ultraviolet.
Sound is about vibration.
The moment a sound is produced, it is energy and it vibrates the air. Sound waves are a product of vibration. No sound can be produced with vibration. The sound that comes from mouth is due the vibration of diaphragm in our throat. Human ears are capable of hearing the sound waves with frequency ranging between 20 to 20,000 hertz. As there is invisible spectrum of light there is this inaudible spectrum of sound. Just visualize the air as a series of molecules in a pack in a pipeline, as the sound wave hits the first molecule, it pushes the second and so on and so forth till the energy of the force gets transmitted to the number of molecule in that series, say the last molecule. Someone standing beyond that molecule cannot hear the sound; the sound which took a birth at the first molecule dies at the last molecule. In essence it is merely mechanical in nature whereas the movement of light is electromagnetic in nature.
Robert Boyle, the first person to discover that sound needs a medium. We all have studied his famous experiment in our schools when the entire air was pumped out of the jar with the alarm clocking ringing but no sound to hear.
What is this spectrum of light?
The electromagnetic spectrum comprise of the visible part and the invisible part. The invisible parts are on both sides the visible part. One end of the spectrum represents the long wavelength known as radio waves and the other end represents the short wavelength known as gamma waves. One end of the visible part ends with infrared and the other end of the visible parts ends with ultraviolet. The end that has infrared is next to the red light and the end that is next to the ultraviolet is violet. In between the visible part are the blue, green, yellow and orange lights. In between the infrared and the radio waves are the micro waves and in between the ultraviolet and the gamma waves are the X-ray.
What are the properties of sound wave?
Sound waves lose energy as it travels through the medium and the loss of energy depends on the type of medium it travels. The sound waves have two vital attributes that makes it define its behavioral properties and those are known as amplitude and frequency. There is a fundamental wave with a particular amplitude and frequency. And beyond that rest all are known as harmonics. What we call as higher pitch as high frequency and lower pitch as low frequency and similarly what we hear as loud sound as high amplitude and the feeble sound as low amplitude. It is interesting to analyze the sounds that come from different musical instruments.
Is it that sound with same frequency and amplitude hear the same?
Not exactly, let’s take the example of gentle movement of finger on the keyboards to piano to the fingers on the strings of the violin, why we hear the sound differently even though they have the same properties. These properties of waves allow it to carry the sound energy from one place to another. There are transmitters and receivers, the sound signals as radio or micro waves when transmitted from location gets received in another location.
Light is an electromagnetic wave.
Radio waves are also light but belong to the invisible part of the light.
The difference is in the frequency and the wavelength.
Sun is the ultimate source of light. It has been the prime source of light for billions of years. The light reaches us through the process of radiation. The sun light reaches us as solar radiation that includes both the visible and the invisible light. Sun light travels at the speed of light and it takes 8 mins and 20 seconds to be precise to cover the distance of 149.6 million kilometers.
In 1838, Friedrich Bessel established light year as the measurement of the distance between sun and earth.
Lets take the simple example of talking on a landline phone, how the sound gets transmitted from one end to the other end. The moment we speak the voice makes the air to vibrate and the vibrating energy carries the sound energy into the phone. It is the diaphragm in the mouthpiece that coverts the sound energy into electrical energy. It is this electrical energy that travels through the wire and reaches the other end where the process gets reversed, the electrical energy gets converted into the sound energy in the microphone. And in the space talking face to face it travels through the molecules of air, since distance is barrier to talking face to face phones have broken those barriers and voice are connected through the power of mobile phones.
There are naturally occurring radio waves like lightning and there are artificially generated radio waves like communication broadcasting. The radio waves travels at the speed of light. There is a transmitter and a receiver. When radio waves arrive at the receiver the electron vibrates inside it resulting in the production of electric current that reproduces the original sound signals. The complete programme of radio to television broadcasting is entirely dependent on the compact power of light and sound show.
It is impossible to imagine a world without the light to enlighten us and the sound to subtly break the uncanny silence of life. We are mere actors playing our part. The roles are diverse. The goal remains intact.
The stage changes…the show continues.
We all come and go but the show must go on…and it this fascinating display of colorful light and the musical notes of sound.
Nihar R Pradhan