What Is Color? | Physics in Motion

GPB Education

11 Feb 201909:38

EducationalLearning

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TLDRThis episode of 'Physics in Motion' explores the science behind color, explaining how objects absorb and reflect specific wavelengths of light to create the visible spectrum. It delves into the primary colors of light—red, green, and blue—and how their combination forms white light, contrasting with the primary pigment colors. The episode also covers the concepts of additive and subtractive color mixing, the role of pigments and dyes, and the biological aspects of how our eyes perceive color through rods and cones. Finally, it touches on the importance of color in nature for signaling and survival.

Takeaways

🌈 Color is a part of the visible spectrum of the electromagnetic spectrum that we can see.
🔍 Objects display colors by reflecting certain wavelengths of light while absorbing others.
📏 The spectrum of color ranges from violet to red with each color having a specific wavelength, from the shortest violet to the longest red.
👀 Human vision can perceive wavelengths from approximately 390 to 790 nanometers.
🎨 The estimated number of colors that humans can distinguish is 18 decillion, which is 18 followed by 33 zeroes.
🟠🔵🟢 The primary colors of pigments are red, blue, and yellow, whereas the primary colors of light are red, green, and blue.
🤩 When the primary colors of light (red, green, and blue) are mixed, they produce white light, which is the combination of all visible colors.
🌞 We perceive color when white light is refracted or bent, distributing wavelengths along a spectrum similar to a rainbow.
🌿 Leaves appear green because they reflect the green wavelength of light and absorb all other colors, facilitated by chlorophyll.
🎨🔄 Additive color mixing involves overlapping wavelengths from different parts of the visible spectrum to create a wide range of colors.
⚪️ Complementary colors in additive color mixing, when combined, produce white light, such as green and magenta, blue and yellow, and red and cyan.

Q & A

What is color in the context of the electromagnetic spectrum?
-Color is the part of the electromagnetic spectrum that we can see, known as the visible spectrum. It is the result of objects absorbing some wavelengths of light and reflecting others, which our eyes perceive as color.
How does the human eye perceive different colors?
-The human eye perceives different colors through the visible spectrum, which ranges from about 390 to 790 nanometers. Each color has a specific wavelength, with red having the longest and violet the shortest.
What are the primary colors of light?
-The primary colors of light are red, green, and blue. When these colors are mixed in equal intensities, they produce white light.
How many colors can the human eye distinguish?
-It is estimated that the human eye can distinguish between 18 decillion colors, which is 18 followed by 33 zeroes.
What is the difference between the primary colors of pigments and light?
-The primary colors of pigments are red, blue, and yellow, which are substances that add color to materials. In contrast, the primary colors of light are red, green, and blue, which are specific wavelengths of light.
What is the relationship between white light and the colors of the visible spectrum?
-White light is not a color itself but is the presence of all the colors of the visible spectrum. It is produced when all the wavelengths of the visible spectrum are combined.
What is the role of chlorophyll in plants and how does it relate to color perception?
-Chlorophyll is a light-trapping pigment involved in photosynthesis, the process by which plants make nutrients from light. It absorbs red light, which is most effective for making glucose, and reflects green light, which is why leaves appear green.
What is the difference between translucent, transparent, and opaque materials in terms of light transmission?
-Translucent materials allow some but not all light to pass through, making objects behind them not clearly visible. Transparent materials allow all light to pass through, making objects clearly visible. Opaque materials do not allow any light to pass through.
What is luminance and how is it measured?
-Luminance is the measure of brightness, or the amount of light reflected off a surface. It is measured in candelas per square meter.
How does additive color mixing work with light?
-Additive color mixing involves overlapping different wavelengths of light from the visible spectrum to create a wide range of colors. When all three primary colors of light (red, green, and blue) are combined, they produce white light.
What is subtractive color mixing and how does it differ from additive color mixing?
-Subtractive color mixing occurs with pigments or dyes, where materials reflect and absorb light. Unlike additive color mixing, which involves combining light, subtractive mixing involves absorbing light, and the resulting color is what is reflected after some wavelengths are absorbed.
How do our eyes perceive light and color?
-Our eyes perceive light and color through rods and cones, which are photoreceptor nerve cells. Rods are more sensitive to light but not to color, while cones are responsible for color perception, transmitting information about wavelengths to our brain.

Outlines

00:00

🌈 Understanding Color and Light

This paragraph explores the concept of color as part of the visible electromagnetic spectrum and how it works. It explains that color is a result of objects absorbing certain wavelengths of light and reflecting others, which our eyes perceive. The visible spectrum ranges from violet to red, each with a specific wavelength. Human eyes can perceive wavelengths from approximately 390 to 790 nanometers, allowing us to distinguish between an estimated 18 decillion colors. The primary colors of light—red, green, and blue—combine to form white light, which is the presence of all colors in the visible spectrum. Isaac Newton's work on the dispersion of light into a spectrum is highlighted, as well as the concept of black as the absence of light. The paragraph also touches on the properties of light, such as refraction, which creates the spectrum seen in a rainbow, and the different types of materials light can pass through, like translucent glass that diffuses light.

05:03

🎨 The Science of Color Mixing

This paragraph delves into the science behind color mixing, both additive and subtractive. Additive color mixing involves combining wavelengths of light to create a wide array of colors, with the primary colors of light—red, green, and blue—being combined to produce white light. The secondary colors of light, which are yellow, magenta, and cyan, are formed by combining two primary colors. The concept of complementary colors, which when combined produce white light, is also discussed. Subtractive color mixing is explained as the process where materials reflect and absorb light, with pigments and dyes absorbing certain wavelengths and reflecting others, leading to the colors we see. The paragraph further explains how too much mixing of pigments can lead to a black color due to absorption of all wavelengths. It also covers the human eye's perception of color through rods and cones, the use of color in nature for various purposes, and provides resources for further learning through the 'Physics in Motion' toolkit.

Mindmap

Keywords

💡Electromagnetic Spectrum

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. It is a fundamental concept in physics that includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. In the context of the video, the visible spectrum is the small portion of the electromagnetic spectrum that human eyes can perceive, which is responsible for the colors we see. The video uses the example of All Saints' Church window to illustrate how the visible spectrum allows us to see the colors in our environment.

💡Visible Spectrum

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. It ranges from violet to red, with each color corresponding to a specific wavelength of light. The video explains that the visible spectrum is what allows us to see colors when light is reflected off objects. For instance, when looking at the church window, the script mentions that the colors we see are the wavelengths of light that are not absorbed by the glass and are instead reflected back to our eyes.

💡Wavelength

Wavelength is the distance between two consecutive points in a wave that are in the same phase. In the script, it is used to describe the colors in the visible spectrum, with red light having the longest wavelength and violet the shortest. The video mentions that human sight can perceive wavelengths from about 390 to 790 nanometers, which is the range of the visible spectrum. Wavelengths are crucial for understanding color because different wavelengths correspond to different colors that we see.

💡Infrared

Infrared is a region of the electromagnetic spectrum that lies just beyond the red end of the visible spectrum. It is characterized by wavelengths longer than those of visible light. The video script explains that beyond the visible spectrum's red end is the infrared region, which is not visible to the human eye but plays a significant role in various applications such as thermal imaging and remote controls.

💡Ultraviolet

Ultraviolet (UV) light is a region of the electromagnetic spectrum with wavelengths shorter than those of violet light but longer than X-rays. It is also not visible to the human eye. In the video, ultraviolet light is mentioned as being just beyond the violet end of the visible spectrum. The script uses the term to illustrate the range of light that exists outside of human visibility.

💡Primary Colors

Primary colors are the fundamental colors from which all other colors can be created through mixing. In the context of pigments, the primary colors are red, blue, and yellow, while for light, they are red, green, and blue. The video script explains that mixing the primary colors of light results in white light, demonstrating the additive nature of light. This concept is central to understanding both color perception and the technology behind devices like color televisions and computer monitors.

💡White Light

White light is a combination of all the colors of the visible spectrum. It appears white to our eyes because it contains all the wavelengths of visible light. The video script mentions Isaac Newton's discovery that white light is composed of a spread-out spectrum of wavelengths, and it is not a color in itself but the presence of all colors. This concept is exemplified when the script describes the mixing of red, green, and blue light to produce white light.

💡Black

Black is the absence of light or the complete absorption of all wavelengths of light. In the video, black is described as what we see when there is no light present. This concept is important for understanding color in terms of both light and pigments, as it contrasts with white light, which contains all colors.

💡Refraction

Refraction is the bending of light as it passes from one medium to another with a different refractive index. The video script explains that we see color when white light is refracted, which causes the different wavelengths to spread out and form a spectrum, like in a rainbow. This phenomenon is essential for understanding how colors are separated and how we perceive them in various natural and artificial light sources.

💡Translucence

Translucence refers to the property of a material that allows light to pass through it, but not clearly. The video script uses the example of the church window glass, which is described as translucent because it diffuses or spreads out the light, making objects on the other side not clearly visible. This concept is important for understanding how different materials interact with light and affect our perception of color and brightness.

💡Luminance

Luminance is a measure of the brightness of a surface, expressed in candelas per square meter. It is related to the amount of light that is reflected off a surface. In the video script, luminance is used to describe how the brightness of a painting changes when light is shone upon it. The script also explains that luminance decreases with the square of the distance from the light source, which is a key concept in understanding how light and color interact in different environments.

💡Chlorophyll

Chlorophyll is a green pigment found in plants that is essential for photosynthesis, the process by which plants convert light energy into chemical energy to fuel their growth. The video script explains that chlorophyll absorbs red and blue light most efficiently, which is why leaves appear green, as they reflect the green light and absorb other colors. This concept is crucial for understanding the role of color in biological processes and the natural world.

💡Additive Color Mixing

Additive color mixing is a process where different colors of light are combined to create a range of colors. In the video script, additive color mixing is demonstrated by combining the primary colors of light—red, green, and blue—to produce various colors, including white light when all three are combined. This principle is fundamental to the way electronic displays and projectors create images.

💡Subtractive Color Mixing

Subtractive color mixing involves the use of pigments or dyes that absorb certain wavelengths of light and reflect others, creating different colors. The video script explains that subtractive mixing is the opposite of additive mixing with light, as it involves the absorption of light rather than its combination. This principle is used in painting and printing, where mixing different pigments can result in a wide range of colors, and mixing all colors can result in black.

💡Pigment

Pigment is a substance that gives color to materials through the selective absorption of certain wavelengths of light. The video script describes pigments as insoluble substances suspended in a medium, such as cadmium sulfide for yellow, chromium (III) oxide for green, and iron (III) oxide for red ochre. Pigments are a key component in the creation of colors in art and various industries.

💡Dye

Dye is a substance that is used to impart color to materials by dissolving in a medium and being absorbed by the material. The video script explains that dyes are often derived from natural sources like plants and insects and have been used for thousands of years. Unlike pigments, dyes are soluble and can transmit color when a material is soaked in them, which is a different method of color application compared to pigments.

💡Rods and Cones

Rods and cones are photoreceptor cells in the retina of the eye that are responsible for vision. The video script mentions that rods are more sensitive to light but do not perceive color, while cones are responsible for color vision. There are approximately 120 million rods and 6 to 7 million cones in the human eye. These cells contain molecules that absorb light, allowing us to perceive the wide array of colors in our environment.

Highlights

All Saints' Church in Atlanta serves as the backdrop to discuss the science behind color.

Color is a part of the electromagnetic spectrum known as the visible spectrum.

Objects absorb certain wavelengths of light and reflect others, which is why we see different colors.

The visible spectrum ranges from violet to red, each with a specific wavelength.

Human sight can perceive wavelengths from about 390 to 790 nanometers.

It's estimated that humans can distinguish between 18 decillion colors.

The primary colors of pigments are red, blue, and yellow, different from the primary colors of light.

Mixing the primary colors of light (red, green, and blue) results in white light.

White light is not a color but the presence of all visible colors of light.

Isaac Newton discovered that white light is made up of a combination of wavelengths.

Black is the absence of light, not a color itself.

Chlorophyll in plants absorbs red light for photosynthesis, reflecting green light and making leaves appear green.

The red edge of the spectrum is where photosynthesis is most active in plants.

Additive color mixing creates a wide range of colors by overlapping different wavelengths of light.

Complementary colors in additive mixing, such as green and magenta, produce white light when combined.

Subtractive color mixing involves pigments and dyes that absorb certain wavelengths, reflecting others to create color.

Pigments are insoluble and change the color of light through selective absorption, while dyes dissolve to transmit color.

The human eye perceives light with rods and cones, which are photoreceptor cells sensitive to light and color.

In nature, color serves as a signal for attraction, repulsion, and camouflage.

The 'Physics in Motion' toolkit offers additional resources for learning about physics.

Transcripts

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