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Light Waves vs. Sound Waves: How Are They Different?

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Light waves vs Sound waves

Light waves and sound waves are types of waves and are both subject to reflection, refraction, and diffraction. However, despite these similarities, the two are different. Light waves are electromagnetic waves that are visible to the eye and can travel through a vacuum. Sound waves are mechanical waves, invisible to the human eye, and unable to travel in a vacuum. Read on for more information on the difference and properties of light and sound waves.

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Overview of Light Waves

Light waves are electromagnetic waves that can be seen by the human eye. They are a form of radiation and are created when electrons are excited and revert to a lower energy state, therefore causing the release of protons. Electromagnetic waves like light waves do not require a medium to travel through, which means that they can pass through a vacuum-like space, as well as through air and the earth’s atmosphere.

light waves seen on long shutter speed
Image Credit: Ahmad Dirini, Unsplash

Types of Light Waves

There are different types of light waves:

  • Radio – Most people think of sound when they hear the term “radio wave” because we listen to sounds coming from the radio. However, radio waves are a form of light wave and are also used in telecommunications and the sending of TV signals.
  • Microwaves – Microwaves are also used for communication and in radar but are most commonly seen in cooking thanks to their ability to generate heat.
  • Infrared Light – Infrared is not visible to the human eye, and it can be felt as heat. Infrared cameras enable viewers to be able to “see” objects according to the amount of infrared that object radiates, effectively letting us see images even in the dark.
  • Ultraviolet – Ultraviolet, or UV, light is another form of light wave that is invisible to the human eye. It is present in sunlight and projected by tanning beds.
  • X-Ray – X-Rays are invisible to the human eye and cannot be felt, but they can pass through solid objects, including the human body. They are most commonly used in hospitals to view bones and skeletal structures.
  • Gamma Rays – Gamma rays have the most energy of any light wave. They are generated by objects like black holes and supernova explosions, and they are used in radiotherapy and, in some cases, sterilization.
  • Visible Light – Visible light rays are the only electromagnetic waves that can be seen by the human eye, and different wavelengths are seen by the human eye as different colors.

How Light Travels

Depending on the frequency of light waves, some can travel through solid objects, while others can travel through liquid and gases. Light is massless, meaning that it can travel through a vacuum, which is why we can see light sources from millions of miles away in the sky.

Image Credit: stux, Pixabay

Light Wave Properties

Light travels in a straight line, but the waves can be refracted, reflected, or diffracted. It travels at the equivalent of 300,000 kilometers per second. This is not only true of all forms of light waves but all electromagnetic waves as well.

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Overview of Sound Waves

Sound waves are mechanical waves and are created by the vibration of objects or matter. These vibrations cause pressure, and it is the waves of pressure that can be heard. Sound waves need some form of medium to be able to propagate and they cannot travel through a vacuum, hence the saying that nobody can hear you scream in space.

woman editing audio in her computer
Image Credit: Kelly Sikkema, Unsplash

Types of Sound Waves

There are three primary types of sound:

  • Infrasonic – Infrasonic is a very low frequency of sound with a frequency of less than 2 hertz. Elephants can communicate hundreds of kilometers using this type of sound.
  • Sonic – Sonic has a frequency less than 20,000 hertz and more than 20 hertz and is generally considered to be the level of sound that humans can hear.
  • Ultrasonic – Ultrasonic sound is very high pitched with a frequency above 20,000 hertz. Bats can hear and communicate using ultrasonic sound.

How Sound Travels

Sound waves are longitudinal waves, which means that the particles of the medium they are traveling through all travel in the same direction. Except in very limited circumstances, all sound waves are longitudinal.

sound wave seen on the screen
Image Credit: Peter Stumpf, Unsplash

Sound Wave Properties

Soundwaves need a medium (something to travel through). This can be a solid, liquid, or gas, and they cannot travel through a vacuum, which means that sound doesn’t travel in space. In the air, sound travels at approximately 332 meters per second, which is approximately 1 million times slower than light.

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Final Thoughts

Light and sound waves are two forms of waves that can be reflected, refracted, and diffracted. However, while light is an electromagnetic wave, sound is a mechanical wave. Light waves are created by the excitement of electrons and sound waves are formed when a medium vibrates.

Featured Image Credit: (L) Jan Huber, Unsplash | (R) Ritupon Baishya, Unsplash

About the Author Robert Sparks

Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.