Light waves, visible and invisible

TED-Ed
19 Sept 201305:58
EducationalLearning
32 Likes 10 Comments

TLDRThe video script explores the concept of color perception and the limitations of human vision. It explains that humans can only see a small portion of the full spectrum of light, which includes invisible light such as radio waves, X-rays, and microwaves. Light is described as electromagnetic radiation that behaves both as a wave and a particle, with different wavelengths and frequencies corresponding to varying energies. The energy of light determines how it interacts with matter, particularly the retina in our eyes. Our retina contains rods for measuring brightness and cones for color perception, which are sensitive to specific energy levels of light. The visible light spectrum, which we can see, ranges from low-energy red to high-energy blue. Special detectors can measure other wavelengths of light that are invisible to the human eye. The script also touches on the broader implications of understanding light, such as using telescopes to observe the universe beyond visible light and applying our knowledge of light physics to study distant celestial bodies.

Takeaways
  • 👀 Humans can only perceive a small part of the full spectrum of light, with our eyes being sensitive to what we call visible light.
  • 🌊 Light behaves as both a wave and a particle, with its properties such as wavelength and frequency determining its energy level.
  • 🌈 The color spectrum we see in a rainbow is a representation of visible light arranged by energy, from low-energy red to high-energy blue.
  • 👁 Our retina contains rods and cones that are sensitive to different energy levels of light, which allows us to perceive various colors.
  • 🚫 Light with energy levels outside the range our retina can measure is invisible to us; it's either too low or too high energy to stimulate the retina.
  • 📡 Radio waves, X-rays, and microwaves are all forms of light with different wavelengths; radio waves have long wavelengths, while X-rays have short wavelengths.
  • 🔍 Special detectors can be used to measure light outside the visible spectrum, acting as 'digital eyes' for humans.
  • ✨ The warmth from a fire, sunlight, ultraviolet light, and artificial light from devices like TVs and microwaves are all forms of electromagnetic radiation.
  • 🌌 The universe emits light across the full spectrum, and to truly see it, we require special telescopes that can detect beyond visible light.
  • 🔭 The Hubble Space Telescope and other space telescopes in orbit allow us to view the universe in parts of the spectrum that are not visible to the naked eye.
  • 🧠 Understanding the physics of light on Earth helps us interpret the light from distant stars and galaxies, providing insights into cosmic phenomena.
Q & A
  • What is the full spectrum of light that humans cannot see?

    -The full spectrum of light includes radio waves, x-rays, and microwaves, among others, which are invisible to the human eye.

  • How does light act both as a wave and a particle?

    -Light exhibits wave-particle duality, meaning it can display properties of both waves (such as wavelength and frequency) and particles (like photons).

  • What determines the energy of a light wave?

    -The energy of a light wave is determined by its wavelength and frequency; shorter wavelengths and higher frequencies correspond to higher energies.

  • How do our eyes perceive colors?

    -Our eyes perceive colors through the stimulation of cone cells in the retina, which are sensitive to different energies of light.

  • What is the visible light spectrum?

    -The visible light spectrum refers to the small range of light with wavelengths that our eyes can detect, from low-energy red light to high-energy blue light.

  • Why can't we see light with wavelengths outside the visible range?

    -We cannot see light outside the visible range because our retina's sensitivity is limited to a specific range of wavelengths and energies.

  • How do special detectors help us measure light outside the visible spectrum?

    -Special detectors, like digital eyes, are designed to be sensitive to different wavelengths of light, allowing us to measure light that our eyes cannot see.

  • What is the significance of using special telescopes to study the universe?

    -Special telescopes allow us to see beyond visible light, capturing the full spectrum of light emitted by celestial bodies, which provides a more comprehensive understanding of the universe.

  • How does the physics of light on Earth help us study distant stars or galaxies?

    -By understanding the physics of different types of light (e.g., x-ray, ultraviolet, microwaves) on Earth, we can interpret the light from distant stars or galaxies to infer the conditions and processes occurring there.

  • What is the relationship between the warmth from a fire, sunlight, and ultraviolet light?

    -The warmth from a fire, the heat from the sun, and the energy from ultraviolet light are all forms of electromagnetic radiation, differing only in their wavelengths and energies.

  • Why is it important to consider the full spectrum of light when studying the natural world?

    -Considering the full spectrum of light helps us understand the complete range of interactions between light and matter, which is crucial for a comprehensive study of the natural world and the universe.

  • How do rods and cones in the retina contribute to our vision?

    -Rods are responsible for measuring brightness, while cones are responsible for color perception. Together, they allow us to perceive the visible light spectrum and interpret the world around us.

Outlines
00:00
👀 The Spectrum of Light: Our Limited Perception

This paragraph explores the concept of human vision and its limitations. It begins by posing a hypothetical scenario where one can only perceive the color red, illustrating the idea that our eyes can only detect a small fraction of the entire light spectrum. The script then explains that light is electromagnetic radiation that exhibits wave-like and particle-like properties. It uses the analogy of ocean waves to describe the varying wavelengths and frequencies of light, which correspond to different energies. The energy of light determines how it interacts with matter, such as the cells in our retina. The visible light, which our eyes can detect, is just a small range of the entire spectrum, and it is defined by the energy levels our retina can sense. The paragraph also discusses the role of rods and cones in our retina, which are responsible for measuring light brightness and perceiving color, respectively. It concludes by emphasizing that while our eyes can't detect light outside the visible spectrum, we can use special detectors to measure these wavelengths, and that the same principles of light apply to the universe, which can be explored using specialized telescopes.

05:00
🌌 Telescopes: Our Window to the Full Spectrum of the Universe

The second paragraph focuses on the role of telescopes in expanding our perception of the universe's light spectrum. It emphasizes that the light we observe from distant celestial bodies is fundamentally the same as the light we experience on Earth, regardless of its wavelength or energy. By understanding the physics of different types of light, such as X-rays and ultraviolet light, we can study and infer the conditions and phenomena occurring in distant stars or galaxies. The paragraph encourages readers to think beyond the limitations of human vision and to appreciate the full spectrum of light that exists around us. It concludes by reminding us that our understanding of the natural world, even if it's just a little, can greatly enhance our perception of the universe.

Mindmap
Keywords
💡Electromagnetic Radiation
Electromagnetic radiation is a form of energy that includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. It travels through space as waves and can also exhibit particle-like properties. In the video, it is the fundamental concept that encompasses all types of light, including those invisible to the human eye, and it is the basis for understanding the full spectrum of light that exists beyond what we can see.
💡Wavelength
The wavelength of a wave is the distance between two successive points that are in the same phase of the wave, such as the distance between two crests. It is a measure of the size of the wave. In the context of the video, different wavelengths correspond to different types of light, from long wavelengths of radio waves to short wavelengths of gamma rays, and it determines the energy and frequency of the light.
💡Frequency
Frequency refers to the number of complete wave cycles that pass a given point in a certain period of time, often measured in Hertz (Hz). It is inversely related to the wavelength; as the wavelength decreases, the frequency increases. In the video, frequency is used to describe how often a wave occurs and is directly related to the energy of the light, with higher frequencies corresponding to higher energies.
💡Visible Light
Visible light is the small portion of the electromagnetic spectrum that is perceptible to the human eye. It has wavelengths ranging from approximately 380 nanometers (violet) to 750 nanometers (red). The video emphasizes that while we perceive this range as light, our eyes are incapable of detecting the broader spectrum of light without the aid of technology.
💡Retina
The retina is the light-sensitive tissue at the back of the eye that contains cells called photoreceptors. It is responsible for converting light into electrical signals that are sent to the brain to create visual images. The video explains that the retina's sensitivity to light with specific energy levels is what allows us to see the visible spectrum of light.
💡Rods and Cones
Rods and cones are the two types of photoreceptor cells in the retina. Rods are responsible for vision in low light conditions and do not mediate color perception, while cones are responsible for color vision and function best in bright light. The video uses rods and cones to explain how the eye can detect different colors based on the energy of the light that stimulates these receptors.
💡Energy
In the context of light, energy refers to the amount of work that the light can perform, which is related to its wavelength and frequency. Shorter wavelengths (higher frequency) correspond to higher energy, while longer wavelengths (lower frequency) correspond to lower energy. The video illustrates how the energy of light determines its interaction with matter, such as the cells in our eyes.
💡Telescopes
Telescopes are instruments that aid in observing distant objects by collecting electromagnetic radiation. The video mentions special telescopes that can detect light beyond the visible spectrum, such as infrared, ultraviolet, and X-rays. These devices allow us to 'see' parts of the universe that are not visible to the naked eye, thus expanding our understanding of celestial phenomena.
💡Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was launched into low Earth orbit and has provided detailed images of the universe in visible and ultraviolet light. The video uses the Hubble Space Telescope as an example of how we can observe and study celestial objects in different parts of the electromagnetic spectrum.
💡Full Spectrum
The full spectrum refers to the complete range of the electromagnetic spectrum, which includes all types of electromagnetic radiation from the longest radio waves to the shortest gamma rays. The video emphasizes the importance of understanding and observing the full spectrum to gain a comprehensive view of the universe and the various forms of light that it emits.
💡Special Detectors
Special detectors, as mentioned in the video, are devices designed to detect and measure electromagnetic radiation outside the range of visible light. These detectors act as 'digital eyes' and enable us to observe and study light that our eyes cannot perceive, such as radio waves, microwaves, and X-rays, thus expanding our understanding of the world and universe.
Highlights

Human eyes can only see a minuscule part of the full spectrum of light, with different kinds of light invisible to us.

Light is electromagnetic radiation that exhibits both wave-like and particle-like properties.

The size of a light wave is referred to as its wavelength, and its frequency is how often the waves occur.

Long wavelengths correspond to low energy, while short wavelengths correspond to high energy.

The retina contains special receptors, rods and cones, which are sensitive to different energy levels of light.

The visible light spectrum that we can see is just a small range of all the light that exists.

The rainbow is an example of visible light arranged in order of increasing energy from red to blue.

Light with energy outside the range our retina can detect is invisible to us.

Radio waves have long wavelengths, while X-rays have short wavelengths, and visible light is in between.

Special detectors can be built to measure light outside the visible spectrum, acting as digital eyes.

The warmth from a fire, sunlight, ultraviolet light, and electromagnetic waves from devices like TVs and microwaves are all forms of light.

The universe emits a full spectrum of light, not just the visible light we see in the night sky.

Telescopes, including the Hubble Space Telescope, allow us to see beyond the visible light spectrum.

There are 20 space telescopes in orbit, each capable of viewing different parts of the light spectrum.

Understanding the physics of light on Earth helps us study celestial objects like distant stars and galaxies.

Light from the universe, regardless of wavelength or energy, is fundamentally the same as the light we experience on Earth.

A little knowledge about the natural world can help us perceive the full spectrum of light around us at all times.

Transcripts
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