Learn about white light. Discover what makes up white light, its spectrum and wavelength, how to turn white light back to its different colors, and its source.
Updated: 11/21/2023
White Light | Definition, Wavelength & Spectrum
Table of Contents
- What is White Light?
- White Light Spectrum
- The Wavelength of White Light
- Sources of White Light
- Lesson Summary
Frequently Asked Questions
How is white light formed?
White light is formed by combining all the frequencies, wavelengths, or colors of the visible light spectrum. Objects that emit white light, such as the sun, stars, or fluorescent bulbs, are emitting all the ranges of frequencies or colors of the visible light spectrum.
What is the average wavelength of white light?
There is no average wavelength of white light, because white light is comprised of all the different wavelengths of the visible light spectrum, i.e., all the colors. If you had to average the nanometer wavelengths of the visible light spectrum it could be the middle of the visible light spectrum which is about 540 nanometers.
What color of the spectrum is white light on?
White light is not an individual color of the spectrum. White light is comprised of all the colors that make up the visible light spectrum.
What exactly is white light?
White light is electromagnetic radiation or waves. White light is comprised of all the frequencies and wavelengths of the visible light spectrum within the electromagnetic spectrum.
Table of Contents
- What is White Light?
- White Light Spectrum
- The Wavelength of White Light
- Sources of White Light
- Lesson Summary
The visible light spectrum exists as frequencies of electromagnetic waves in classical physics, or as oscillating photons in quantum mechanics. The electromagnetic spectrum is comprised of a spectrum of frequencies and wavelengths of electromagnetic radiant energy which includes radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays. Radiant energy travels the speed of light at approximately 300,000 km/s. Visible light is the portion of the electromagnetic spectrum that is detectable by the human eye. It consists of an assortment of frequencies and wavelengths which emerge through the sense of sight as all the colors of the rainbow.
 |
White light and sunlight contain all the wavelengths and frequencies of the visible light spectrum. Isaac Newton and Joseph von Fraunhofer were some thinkers that experimented with light and shined white light through a glass prism. When electromagnetic radiation changes mediums such as moving from air into glass, it changes speed. When the medium it is transitioning too is denser than the medium it started in, light slows down. The different frequencies of light that comprise white light oscillate at different energy levels and therefore slow down to slightly different speeds and change to slightly different trajectories. This causes the white light to separate into its comprising frequencies which emerge as all the colors of the rainbow.
 |
What light is had been debated among scientists for centuries. Scientific thinkers argued about whether light was made up of particles or waves. Light's particle behavior is observed in the photoelectric effect where electrons from the atoms on a surface light shines on randomly increase energy levels as if being randomly impacted by particles. This prompted Einstein to propose that light can be quantized, or that there is a smallest unit or quanta of light, i.e., the photon. Light behaves like a wave in the sense that it propagates around corners and interferes with itself. Thomas Young's double slit experiment confirmed light's exceptionally wave-like properties. When monochromatic light (e.g., a laser) is fired through two very small slits that are right next to each other, the light passing through each slit will propagate and intersect with the light propagating from the other slit. This experiment demonstrates light's wave-like properties as the light propagating from each slit intersect each other, they interfere with each other, just like water waves from two sources on a still pond.
 |
The top of a wave is called a peak, and the valley of a wave is called a trough. Constructive interference occurs when similar points on separate waves intersect, e.g., when the peak of one wave meets the peak of another wave. Destructive interference occurs when opposite points of separate waves meet, e.g., the peak of one wave meeting the trough of another wave; this results in the waves canceling each other out. If two drops of water fall on a still pond, the waves produced by each drop will intersect and create an interference pattern with destructive and constructive interference. Light produces an interference pattern when shined through two slits and projected onto a surface to be observed. When water waves intersect and destructively interfere, there is no wave present, and the water goes flat. Destructive interference with light means there is no oscillation or wave on the electromagnetic field, so there is no light present. This interference pattern results in bright spots or lines fading out in two directions with the lack of light in between them.
 |
 |
To unlock this lesson you must be a Study.com Member.
Create your account
You must cCreate an account to continue watching
Register to view this lesson
Are you a student or a teacher?
Create Your Account To Continue Watching
As a member, you'll also get unlimited access to over 88,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.
Get unlimited access to over 88,000 lessons.
Try it now
It only takes a few minutes to setup and you can cancel any time.
Already registered? Log in here for access
BackResources created by teachers for teachers
Over 30,000 video lessons
& teaching resources‐all
in one place.
I would definitely recommend Study.com to my colleagues. It’s like a teacher waved a magic wand and did the work for me. I feel like it’s a lifeline.
Jennifer B.
Teacher
Back
Your next lesson will play in
10 seconds
Thomas Young's double slit experiment can also be done using sunlight. When sunlight is used, the white light passing through the double slit creates an interference pattern that is comprised of all the frequencies contained within the white light, i.e., all the colors of the rainbow that are detectable by the human eye. Each color of the rainbow is a range of frequencies of electromagnetic waves or photons oscillating at different frequencies. The frequency of the wave or oscillating photon is correlated with its energy level so that E=hf, where energy (E) is equal to the product of plank's constant (h) and the frequency of the wave or photon (f). From lowest energy level to highest, white light is comprised of red, orange, yellow, green, blue, and violet light, and all the colors in between.
 |
What Makes up White Light?
White light shined through a glass prism also results in the separation of the individual frequencies that make up the white light. However, at first it was suggested that the prism itself was causing white light to change into the colors of the rainbow and not that white light was comprised of all the colors. This hypothesis was quickly falsified when the rainbow emerging from one prism was shined into another prism in order recombine the colors. The result was white light emerging from the opposite end of the second prism confirming that white light is made up of the many colors and frequencies of visible light.
The colors of the rainbow can be remembered with the acronym VIBGYOR or ROYGBIV. I.e., Violet, Indigo, Blue, Green, Yellow, Orange, and Red; or the reverse. Each color exists as a range of wavelengths or frequencies of electromagnetic radiation. When white light is shined on an object, the color of the object is observed because it absorbs some frequencies or colors of light and reflects others. For example, an apple is observed as being red because the chemical compounds and elements that make up the skin of the apple mainly reflect frequencies and wavelengths of red light and absorb the others. Different compounds and elements absorb different frequencies of visible light and reflect others when heated to a plasma state.
To unlock this lesson you must be a Study.com Member.
Create your account
The wavelengths of visible light can be measured in nanometers, a unit derived from the SI base unit meters. 1 nanometer is equal to 0.000000001 meters, or one billionth of a meter. The wavelengths and frequencies of the visible light spectrum are listed in the table below:
| Wavelengths in Nanometers |
|---|
Violet|380-450 nm
Blue|450-485 nm
Cyan|485-500 nm
Green|500-565 nm
Yellow|565-590 nm
Orange|590-625 nm
Red|625-700 nm
To unlock this lesson you must be a Study.com Member.
Create your account
White light can come from any source that produces all the visible frequencies of light, such as from the Sun, fluorescent light bulbs, or some stars. Spectrometry is a scientific field that makes observations using the separated frequencies of light. For example, star light can be sent through a prism and broken up into its component frequencies. When the spectrum from the star is magnified, it is observed that some frequencies are missing, and there are gaps in and between colors. When light interacts with the atoms that make up chemical elements, different frequencies of light can be absorbed and increase electron energy levels (i.e., the photoelectric effect) depending on the atoms or element. That is, different frequencies of light are absorbed by different elements, and when elements are in a plasma state producing light, they release different frequencies. So, the light that is missing in the broken-up spectrum of a star provides information regarding what elements make up the star. Additionally, if star light passes through the atmosphere of an orbiting planet astronomers can observe what elements make up that planet's atmosphere.
 |
To unlock this lesson you must be a Study.com Member.
Create your account
Overall, white light is comprised of all the different wavelengths and frequencies that make up the visible light spectrum within the electromagnetic spectrum. Different experiments show that light has wave and particle-like properties. Light's wave-like properties are observed in Thomas Young's double slit experiment and through the interference patterns it creates. Light's particle-like properties are observed in the photoelectric effect where light can be thought of as being comprised of photons that randomly impact electrons. Light can be thought of as a quantizable particle-wave that emerges as different colors when oscillating at different frequencies or energy levels. When white light passes through a glass prism, the different oscillating frequencies of waves or photons separate as the light refracts and bends from being slowed down to slightly different speeds. This results in the separation of all the different frequencies that make up white light, i.e., all the colors of the rainbow. Each color of light has a range of different wavelengths and frequencies that are measured in nanometers.
To unlock this lesson you must be a Study.com Member.
Create your account
Video Transcript
Definition of White Light
The electromagnetic spectrum is comprised of a variety of types of electromagnetic waves, each with different wavelengths or frequencies. For example, x-rays, gamma rays, infrared radiation and ultraviolet radiation are examples of electromagnetic waves. Only a small portion of the spectrum of wavelengths can be seen by the human eye. This visible portion of the electromagnetic spectrum is called the visible spectrum. This shows the full spectrum of electromagnetic radiation and highlights the small part of the spectrum that can be called the visible spectrum.
White light is defined as the complete mixture of all of the wavelengths of the visible spectrum. This means that if I have beams of light of all of the colors of the rainbow and focus all of the colors onto a single spot, the combination of all of the colors will result in a beam of white light.
Sources of White Light
White light can be generated by a variety of sources both in space and by artificial sources on earth. For example, the sun and other stars are sources of white light. The sun is the most obvious source of white light in our solar system. As for artificial sources, fluorescent light bulbs and white LEDs produce white light. Other light bulbs, like the incandescent lamp, do not produce white light. They produce light of much longer wavelengths along the yellow to red range.
Spectrum
This illustrates the full electromagnetic spectrum. It highlights just how small the visible spectrum is as compared to the rest of the electromagnetic spectrum. White light is a mixture of all of the visible wavelengths. The full spectrum that forms white light is listed in this table:
| Color | Wavelength |
|---|---|
| Violet | 380-450 nm |
| Blue | 450-495 nm |
| Green | 495-570 nm |
| Yellow | 570-590 nm |
| Orange | 590-620 nm |
| Red | 620-750 nm |
Let's discuss a few key points concerning the visible spectrum, starting with absorption and reflection. Here are a few fun facts about colors and white light. When our eyes detect the color of an object, that means that all other colors of the spectrum were absorbed by the object except for the color you see. For example, when you see a blue shirt, every color except blue was absorbed by the shirt (as a result of pigment molecules of the shirt or any object for that matter). An extreme case would be the color black. When we see black objects, that means that all of the colors of the spectrum were absorbed by the object; hence, nothing is reflected and we see black. Conversely, when we see a white object that means none of the colors of the visible spectrum were absorbed by the object; they were all reflected off the object, and the mixture of those reflected colors gives rise to the white pigment of the object.
Now let's discuss prisms and rainbows. Another interesting thing about white light is that it can be split up into its individual colors. A prism is a device that can separate white light into its different colors. When white light goes through a prism, the light bends because the speed of light decreases as it goes from air to the prism. The speed of light depends on the wavelength of the light. As a result, when white light bends through a prism, each wavelength travels at a different speed inside the prism, resulting in the different colors emerging from the prism. This is the same reason why we have rainbows. The white light from the sun bends through the drops of rain, which act like many tiny prisms. As a result, each of the white beams of light going through the rain separate into the different colors and, collectively, they combine to form a rainbow.
Lesson Summary
The electromagnetic spectrum is comprised of a variety of types of electromagnetic waves, each with different wavelengths or frequencies. For example, x-rays, gamma rays, infrared radiation and ultraviolet radiation are examples of electromagnetic waves. Only a small portion of the spectrum of wavelengths can be seen by the human eye. This visible portion of the electromagnetic spectrum is called the visible spectrum.
When you mix all of the wavelengths of the visible spectrum, you get white light. The sun and many objects in space are good natural sources of white light. On earth, fluorescent light bulbs and white LEDs are artificial sources of white light. Devices like prisms can be used to separate white light back into the different colors of the visible spectrum.
Key Terminology from the Lesson
 |
- Electromagnetic Spectrum: variety of differing electromagnetic wavelengths/frequencies
- Visible Spectrum: those wavelengths that can be seen by the 'naked eye'
- White Light: the combination of all the visible wavelengths
Learning Outcomes
Study this lesson thoroughly so that you can:
- State the definition of white light
- Identify sources of white light
- Recognize the electromagnetic spectrum
To unlock this lesson you must be a Study.com Member.
Create your account
Register to view this lesson
Are you a student or a teacher?
Unlock Your Education
See for yourself why 30 million people use Study.com
Become a Study.com member and start learning now.
Become a MemberAlready a member? Log In
BackResources created by teachers for teachers
Over 30,000 video lessons
& teaching resources‐all
in one place.
I would definitely recommend Study.com to my colleagues. It’s like a teacher waved a magic wand and did the work for me. I feel like it’s a lifeline.
Jennifer B.
Teacher
Back
White Light | Definition, Wavelength & Spectrum
Related Study Materials
Explore our library of over 88,000 lessons
Browse by subject