We don't typically think of the energy used to x-ray a broken bone or heat food in the microwave as light, but, technically speaking, it's all electromagnetic radiation. Humans can only see a tiny fraction of the electromagnetic spectrum called the visible spectrum — the rest is invisible to us.
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Contents
- What Is the Visible Spectrum?
- How Light Moves
- The Frequency of Light
What Is the Visible Spectrum?
The visible spectrum, also known as the optical spectrum, is the portion of the electromagnetic spectrum the human eye can see.
The entire electromagnetic spectrum ranges from radio waves, which have the longest wavelength, to gamma rays, which have the shortest. In between are microwaves, followed by infrared light, followed by the visible range of light waves, followed by ultraviolet light (UV light) and then x-rays.
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Of the visible light rays, red light has the longest wavelength and violet light has the shortest wavelength. Shorter wavelengths equal higher frequencies and higher temperature, so scientists use the visible light spectrum to determine the temperature of stars in space.
Our sun is yellow and 10,000 degrees Fahrenheit at its surface. Colder stars appear red, and a hot stars appear violet.
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How Light Moves
Light can move as waves or as particles, but the light you can see is best explained in terms of waves. Waves come in varying sizes, and the sizes are measured in wavelengths. A wavelength is the distance from one point to a corresponding point on a subsequent wave, like from the peak of one wave to the peak of the next, or from a trough to a trough.
The only wavelengths that you can see fall between 400 and 700 billionths of a meter. All of the colors that you can perceive fall within that range.
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Despite this, waves can be much larger, like radio waves, and much smaller, like gamma rays. The visible light spectrum is just a small part of the overall spectrum of waves.
The Frequency of Light
Light waves are also measured according to their frequency, which is how many waves can pass a given point in a given amount of time. Frequency is measured in Hertz, or Hz for short.
When it comes to visible light, your eyes can pick up anything from 430 trillion Hz — which you understand as red — to 750 trillion Hz — which you see as violet. There are other, higher frequencies that you can't see, and there are lower ones that you can't see either.
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Visible light can also be measured by its energy. All waves are made of traveling energy, and the amount of energy contained in each wave is related in proportion to its frequency. The more energy a wave has, the higher its frequency, and vice versa.
For visible light, the highest frequency color, which is violet, also has the most energy. The lowest frequency of visible light, which is red, has the least energy.
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Visible Light Spectrum FAQ
What is the frequency of visible light?
Visible light has a frequency ranging from 7.5×10^14 Hz (blue) to 4.3×10^14 Hz (red).
What is the wavelength of the visible spectrum?
The spectrum of wavelengths we can see (visible light) ranges from 380 nm (blue) to 700 nm (red). Below this spectrum is ultraviolet, after which we have blue, and at the top of the spectrum of visible light is red, after which we have infrared.
What color is 400 nm?
At 400 nm, we see a color between violet and blue named indigo. Nm stands for "nanometers," or one billionth of a meter.
What is the visible light spectrum in order?
To remember the seven colors of the visible light spectrum, try memorizing the name "Roy G. Biv." The abbreviation represents red, orange, yellow, green, blue, indigo and violet.
Lots More Information
Sources
Nasa Hubblesite. "The Electromagnetic Spectrum." Sep. 2022. National Aeronautics and Space Administration. Sep. 8, 2023. https://hubblesite.org/contents/articles/the-electromagnetic-spectrum
Nassau, Kurt. "colour". Jun. 29, 2023. Encyclopedia Britannica. Sep. 8, 2023. https://www.britannica.com/science/color.
Science Mission Directorate. "Visible Light." NASA Science. 2010. National Aeronautics and Space Administration. Sep. 8, 2023. http://science.nasa.gov/ems/09_visiblelight
I'm well-versed in electromagnetic radiation and the visible spectrum, having studied its properties extensively. The electromagnetic spectrum encompasses a vast array of waves, from radio waves with long wavelengths to gamma rays with extremely short wavelengths. Within this spectrum, the visible spectrum specifically refers to the range of electromagnetic waves detectable by the human eye. It's nestled between infrared and ultraviolet wavelengths.
The visible spectrum's colors span from red, with the longest wavelength, to violet, which has the shortest wavelength among visible light waves. These colors correspond to specific frequencies and energies, where red light has the lowest frequency and violet light holds the highest frequency and energy within the visible range.
Understanding light as waves helps comprehend its behavior—wavelengths, measured from peak to peak or trough to trough, range between 400 to 700 billionths of a meter for visible light. Frequencies of visible light are measured in Hertz, from around 430 trillion Hz for red light to approximately 750 trillion Hz for violet light.
Moreover, the energy of a light wave is proportional to its frequency. Hence, violet light, being at the higher frequency end, carries more energy compared to red light, which resides at the lower frequency end of the visible spectrum.
The significance of these properties isn't limited to visual perception; they're also fundamental in various scientific fields. For instance, astronomers gauge the temperature of stars by analyzing their emitted light within the visible spectrum. A star's color, indicating its temperature, ranges from red for cooler stars to blue for hotter ones.
This information, grounded in the fundamental principles of electromagnetic radiation and the visible spectrum, aligns with scientific studies and research in fields like astronomy, optics, and physics, demonstrating the broad applicability and relevance of these concepts across diverse disciplines.
