Why Do We See Colors?

But Why?
24 Apr 202009:13
EducationalLearning
32 Likes 10 Comments

TLDRThis script delves into the science behind why humans perceive only a limited range of colors. It explains that our vision evolved to detect the most abundant light from the sun, which is in the visible spectrum. The script also explores the complex process of light interacting with our eyes' cells, leading to the perception of color. It touches on the existence of tetrachromats, who possess an additional color receptor and can discern more color nuances. Lastly, it discusses why we don't see ultraviolet light, which is less relevant to human survival and is often overshadowed by visible light.

Takeaways
  • 👀 Humans evolved to see colors that are most abundant in the visible light spectrum, which is primarily emitted by the Sun.
  • 🌞 The visible spectrum is just a small part of the entire electromagnetic spectrum, and most of the Sun's light is within the visible range.
  • 🔍 Our eyes contain specialized cells called rods and cones, which act like antennas to detect light through pigment proteins called opsins.
  • 🛑 The process of vision begins when light interacts with retinol in the opsin proteins, triggering a series of biochemical reactions that signal the brain.
  • 🧠 The brain interprets color by comparing the activation levels of different types of cones, which are sensitive to specific wavelengths of light.
  • 🎨 There are individuals, known as tetrachromats, who possess an additional cone and can detect more color variations than the average person.
  • 🌈 Tetrachromats do not see entirely new colors but can discern more shades and hues within the colors that others can see.
  • 🌺 Bees can see ultraviolet light, which helps them identify flowers among a field of yellow, a trait not necessary for humans.
  • 🌞 Ultraviolet light at shorter wavelengths is absorbed by the cornea and other parts of the eye, reducing its visibility even if humans could perceive it.
  • 🚫 Humans do not see most light waves because they would be overwhelmed by the intensity of visible light, suggesting an evolutionary reason for our limited color vision.
  • 🌟 If there was a survival advantage to seeing additional parts of the spectrum, such as ultraviolet light, it is likely that humans would have evolved to do so.
Q & A
  • Why do humans only see a combination of three colors?

    -Humans see a combination of three colors because we evolved to have three types of cone cells in our eyes, each sensitive to different wavelengths of light (red, green, and blue). This allows us to perceive a wide range of colors through the combination of these three signals.

  • What is the visible spectrum of light?

    -The visible spectrum of light is the small portion of the electromagnetic spectrum that can be seen by the human eye, ranging approximately from 400 to 700 nanometers in wavelength.

  • Why is it beneficial for humans to be sensitive to the visible spectrum of light?

    -It is beneficial because the Sun emits most of its radiation within the visible spectrum, making it the most abundant and useful type of light for us to detect in our environment.

  • What are rods and cones in the human eye?

    -Rods and cones are photoreceptor cells in the human retina. Rods are responsible for vision in low light conditions, while cones detect color and are active in brighter light.

  • How do opsins and retinol work together in photoreception?

    -Opsins are proteins in the membranes of photoreceptor cells that bind to retinol. When retinol absorbs a photon of light, it changes shape, which in turn changes the shape of the opsin protein, triggering a series of biochemical reactions that ultimately signal the presence of light to the brain.

  • Why do we see colors as combinations of red, green, and blue signals?

    -We see colors as combinations of red, green, and blue signals because each type of cone cell in our eyes is sensitive to a specific range of wavelengths. The brain interprets the ratios of activation from these three types of cones to determine the color.

  • What is a tetrachromat?

    -A tetrachromat is an individual who possesses four types of cone cells instead of the usual three, allowing them to see a wider range of color hues and shades than most people.

  • Why don't humans see ultraviolet light like bees do?

    -Humans don't see ultraviolet light because our eyes have evolved to filter it out, with the cornea and lens absorbing most UV light to protect the retina. Additionally, the abundance of visible light makes it unnecessary for us to detect UV light for survival.

  • What is the role of glutamate in the process of vision?

    -Glutamate is an excitatory neurotransmitter released by photoreceptor cells. When light reduces the amount of glutamate released, it signals to neighboring neurons that light has been detected, contributing to the process of visual signal transmission to the brain.

  • How does the brain determine the intensity and frequency of light entering the eye?

    -The brain determines the intensity and frequency of light by comparing the relative activation levels of the different types of cone cells. The ratios of these activations help pinpoint the specific wavelength and intensity of the light.

Outlines
00:00
👀 Evolution of Human Color Vision

This paragraph delves into why humans perceive a limited range of colors, despite the vast electromagnetic spectrum. It explains that our ability to see specific colors is a result of evolution, where our sensitivity to light is primarily to the light emitted by the Sun, which is predominantly in the visible spectrum. The Planck spectrum is introduced to illustrate that the sun's light aligns with the visible spectrum, suggesting that our visual sensitivity is adapted to the most abundant light source on Earth. The paragraph also touches on the possibility of other light frequencies existing but being overshadowed by the visible light due to their relative scarcity.

05:01
🌈 Understanding the Human Eye's Light Interaction

This paragraph explains the biological process behind how we see colors. It describes the role of rods and cones in our eyes, which act as 'antennas' by interacting with light through opsins and retinol. The paragraph details the chemical reactions initiated when light hits these photoreceptors, leading to the generation of signals sent to the brain. It also discusses how color perception occurs as our brain deciphers the frequencies of light by comparing the excitation levels of different cones, each sensitive to specific wavelengths. The explanation includes the concept of tetrachromats, individuals with an additional color receptor, who can distinguish more color nuances than the average person. Lastly, it addresses why humans do not see ultraviolet light, which is less abundant and often absorbed by the cornea, suggesting that our visual capabilities are well-adapted to our needs and environment.

Mindmap
Keywords
💡Visible Spectrum
The visible spectrum refers to the range of wavelengths of light that are visible to the human eye. In the video, it is mentioned as a small sliver of the entire electromagnetic spectrum, which is significant because it highlights why humans are only sensitive to a specific portion of light. The script explains that the Sun emits most of its light in the visible spectrum, which is why our eyes have evolved to detect this range of light.
💡Planck Spectrum
The Planck spectrum is the distribution of electromagnetic radiation emitted by a black body at a given temperature, in this case, the Sun. The script uses the Planck spectrum to illustrate that most of the Sun's light is produced in the visible range, which is why our eyes are adapted to perceive this spectrum. This concept is central to understanding why humans see the colors they do.
💡Rods and Cones
Rods and cones are photoreceptor cells in the retina of the eye that are responsible for vision. The script explains that rods are sensitive to low light levels, while cones are responsible for color vision. The presence of these 'antennae' in our eyes allows us to detect light and interpret it as color, which is essential for understanding how we perceive the world around us.
💡Opsins
Opsins are pigment proteins found in the membranes of rods and cones. They are crucial for the process of phototransduction, which is how our eyes convert light into electrical signals that the brain can interpret. The script describes how variations in opsin proteins lead to the absorption of specific wavelengths of light, which is key to our ability to see different colors.
💡Retinol
Retinol is a chromophore that is bound to the opsin protein and acts as the light-sensitive component in our photoreceptors. The script explains that when a photon of the correct frequency hits retinol, it changes shape, triggering a cascade of events that lead to the perception of light. This process is fundamental to how we see colors and interpret the visual world.
💡Tetrachromats
Tetrachromats are individuals who possess four unique cones or color receptors, as opposed to the usual three found in most humans. The script mentions that some women may have this trait, which allows them to detect differences in color more acutely than others. This concept is important for understanding the range of human color perception capabilities.
💡Color Perception
Color perception is the process by which the brain interprets the signals from the cones in the eye to discern different colors. The script explains that our brains use the relative excitation of different cones to compare ratios and determine the frequency of light entering our eyes. This process is central to how we experience the colorful world around us.
💡Ultraviolet Light
Ultraviolet light is a type of electromagnetic radiation with a wavelength shorter than that of visible light but longer than X-rays. The script discusses why humans do not perceive ultraviolet light, which is due to its rapid absorption by the cornea and the fact that it would be drowned out by visible light under normal conditions. This concept is relevant to understanding the limitations of human vision.
💡Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The script mentions that ultraviolet light at 300 nanometers is rapidly absorbed by the cornea, losing much of its intensity. This absorption is a key factor in why humans do not see ultraviolet light, illustrating the role of the cornea in filtering light.
💡Evolution
Evolution is the process by which species adapt and change over time through natural selection. The script suggests that the reason humans see specific colors is due to evolutionary adaptation to the light spectrum provided by the Sun. It also implies that if seeing more colors or ultraviolet light had been beneficial, humans might have evolved to perceive those as well.
Highlights

Humans see a limited range of colors due to evolution and the specific light wavelengths the sun emits.

The visible spectrum is a small portion of the electromagnetic spectrum, with most of the sun's light in the visible range.

Light interacts with charged cells in our eyes, specifically rods and cones, which signal the brain about the presence of light.

Opsins and retinol in our eyes act as antennas, responding to specific light frequencies and initiating a signal to the brain.

The process of light interacting with our eyes involves a complex biochemical chain reaction leading to the perception of light.

Color perception is the brain's interpretation of the frequencies of light, comparing the excitation of different cones.

Humans have three types of cones, each sensitive to a specific wavelength, allowing us to perceive a wide range of colors.

Tetrachromats, who possess a fourth color receptor, can detect more color differences but not necessarily perceive entirely new colors.

The fourth cone in tetrachromats is likely a mutation of the green cone, with a slightly shifted absorption spectrum.

Bees can see ultraviolet light, which is important for identifying flowers, but humans do not due to the abundance of visible light.

Ultraviolet light is rapidly absorbed by the cornea, reducing its intensity and making it difficult for humans to perceive.

The human eye is adapted to perceive the most abundant radiation on Earth, which is visible light.

The complexity of the human eye's response to light is a testament to the intricate mechanisms of evolution.

The inability to see ultraviolet light is not a significant loss, as it would be overshadowed by the visible spectrum.

Evolution has shaped our visual capabilities to be most effective in our environment, prioritizing the perception of visible light.

The video explores the biological and evolutionary reasons behind the specific colors and light wavelengths humans can perceive.

Transcripts
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