Light waves, visible and invisible - Lucianne Walkowicz
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0:07 - 0:10What if you could only see one color?
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0:10 - 0:12Imagine, for instance,
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0:12 - 0:14that you could only see things that were red
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0:14 - 0:15and that everything else
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0:15 - 0:17was completely invisible to you.
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0:17 - 0:18As it turns out,
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0:18 - 0:20that's how you live your life all the time
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0:20 - 0:22because your eyes can only see
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0:22 - 0:25a minuscule part of the full spectrum of light.
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0:25 - 0:28Different kinds of light are all around you everyday
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0:28 - 0:30but are invisible to the human eye,
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0:30 - 0:33from the radio waves that carry your favorite songs,
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0:33 - 0:35to the x-rays doctors use to see inside of you,
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0:35 - 0:38to the microwaves that heat up your food.
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0:39 - 0:40In order to understand
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0:40 - 0:41how these can all be light,
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0:41 - 0:43we'll need to know a thing or two
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0:43 - 0:44about what light is.
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0:44 - 0:47Light is electromagnetic radiation
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0:47 - 0:49that acts like both a wave and a particle.
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0:49 - 0:52Light waves are kind of like waves on the ocean.
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0:52 - 0:54There are big waves and small waves,
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0:54 - 0:56waves that crash on the shore
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0:56 - 0:57one right after the other,
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0:57 - 1:00and waves that only roll in every so often.
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1:00 - 1:03The size of a wave is called its wavelength,
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1:03 - 1:04and how often it comes by
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1:04 - 1:06is called its frequency.
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1:07 - 1:09Imagine being a boat in that ocean,
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1:09 - 1:11bobbing up and down as the waves go by.
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1:11 - 1:14If the waves that day have long wavelengths,
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1:14 - 1:16they'll make you bob only so often,
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1:16 - 1:18or at a low frequency.
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1:18 - 1:20If the waves, instead, have short wavelengths,
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1:20 - 1:21they'll be close together,
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1:21 - 1:24and you'll bob up and down much more often,
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1:24 - 1:25at a high frequency.
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1:25 - 1:28Different kinds of light are all waves,
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1:28 - 1:30they just have different wavelengths and frequencies.
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1:31 - 1:33If you know the wavelength or frequency
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1:33 - 1:34of a wave of light,
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1:34 - 1:37you can also figure out its energy.
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1:37 - 1:39Long wavelengths have low energies,
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1:39 - 1:41while short wavelengths have high energies.
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1:41 - 1:43It's easy to remember
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1:43 - 1:45if you think about being in that boat.
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1:45 - 1:46If you were out sailing on a day
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1:46 - 1:48with short, choppy waves,
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1:48 - 1:50you'd probably be pretty high energy yourself,
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1:50 - 1:54running around to keep things from falling over.
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1:54 - 1:55But on a long wavelength sea,
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1:55 - 1:57you'd be rolling along, relaxed,
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1:57 - 1:58low energy.
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1:59 - 2:01The energy of light tells us
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2:01 - 2:03how it will interact with matter,
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2:03 - 2:05for example, the cells of our eyes.
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2:05 - 2:08When we see, it's because the energy of light
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2:08 - 2:10stimulates a receptor in our eye
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2:10 - 2:11called the retina.
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2:11 - 2:13Our retina are only sensitive to light
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2:13 - 2:15with a very small range in energy,
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2:15 - 2:18and so we call that range of light visible light.
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2:18 - 2:21Inside our retina are special receptors
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2:21 - 2:23called rods and cones.
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2:23 - 2:25The rods measure brightness,
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2:25 - 2:27so we know how much light there is.
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2:27 - 2:30The cones are in charge of what color of light we see
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2:30 - 2:31because different cones are sensitive
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2:31 - 2:33to different energies of light.
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2:33 - 2:35Some cones are more excited by light
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2:35 - 2:38that is long wavelength and low energy,
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2:38 - 2:40and other cones are more excited
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2:40 - 2:43by short wavelength, high-energy light.
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2:43 - 2:44When light hits our eye,
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2:44 - 2:46the relative amount of energy each cone measures
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2:46 - 2:49signals our brain to perceive colors.
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2:49 - 2:50The rainbow we perceive
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2:50 - 2:54is actually visible light in order of its energy.
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2:54 - 2:55At one side of the rainbow
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2:55 - 2:57is low-energy light we see as red,
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2:57 - 3:00and at the other side is high-energy light
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3:00 - 3:02we see as blue.
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3:02 - 3:03If light shines on us
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3:03 - 3:05that has an energy our retina can't measure,
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3:05 - 3:07we won't be able to see it.
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3:08 - 3:10Light that is too short wavelength or high energy
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3:10 - 3:12gets absorbed by the eye's surface
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3:12 - 3:14before it can even get to the retina,
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3:14 - 3:17and light that is too long wavelength
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3:17 - 3:17doesn't have enough energy
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3:17 - 3:20to stimulate our retina at all.
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3:20 - 3:22The only thing that makes one kind of light
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3:22 - 3:24different from another is its wavelength.
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3:24 - 3:26Radio waves have long wavelengths,
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3:26 - 3:29while x-rays have short wavelengths.
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3:29 - 3:31And visible light, the kind you can actually see,
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3:31 - 3:33is somewhere in between.
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3:33 - 3:35Even though our eyes can't detect light
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3:35 - 3:37outside of the visible range,
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3:37 - 3:39we can build special detectors
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3:39 - 3:40that are stimulated
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3:40 - 3:42by these other wavelengths of light,
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3:42 - 3:43kind of like digital eyes.
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3:43 - 3:45With these devices,
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3:45 - 3:46we can measure the light that is there,
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3:46 - 3:49even though we can't see it ourselves.
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3:50 - 3:52So, take a step back and think about
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3:52 - 3:54all of this for a moment.
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3:54 - 3:55Even though they seem different,
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3:55 - 3:57the warmth you feel from a crackling fire
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3:57 - 3:59is the same as the sun shining on you
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3:59 - 4:00on a beautiful day,
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4:00 - 4:02the same as ultraviolet light
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4:02 - 4:04you put on sunscreen to protect yourself from,
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4:04 - 4:06the same thing as your TV,
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4:06 - 4:07your radio,
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4:07 - 4:08and your microwave.
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4:09 - 4:11Now, those examples are all things here on Earth,
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4:11 - 4:14things you experience in your everyday life,
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4:14 - 4:17but here's something even more amazing.
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4:17 - 4:20Our universe gives off the full spectrum of light, too.
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4:21 - 4:22When you think of the night sky,
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4:22 - 4:24you probably think of being able
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4:24 - 4:27to see the stars shining with your own eyes,
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4:27 - 4:28but that's just visible light,
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4:28 - 4:30which you now know is only a tiny part
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4:30 - 4:32of the full spectrum.
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4:32 - 4:33If we had to draw the universe
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4:33 - 4:36and could only use visible light,
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4:36 - 4:37it would be like having only one crayon --
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4:37 - 4:39pretty sad.
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4:39 - 4:42To see the universe in its full spectrum,
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4:42 - 4:43we need to have the right eyes,
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4:43 - 4:45and that means using special telescopes
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4:45 - 4:48that can help us see beyond visible light.
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4:48 - 4:50You've probably heard of the Hubble Space Telescope
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4:50 - 4:52and seen its beautiful pictures
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4:52 - 4:55taken in visible and ultraviolet light.
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4:55 - 4:56But you might not know
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4:56 - 4:58that there are 20 space telescopes in orbit,
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4:58 - 5:00missions that can each see part
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5:00 - 5:02of the full spectrum of light.
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5:02 - 5:05With telescopes acting as our virtual eyes,
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5:05 - 5:07both in space and here on Earth,
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5:07 - 5:09we can see some amazing things.
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5:09 - 5:11And the coolest thing of all,
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5:11 - 5:13no matter the wavelength or energy,
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5:13 - 5:16the light that we see out in the distant universe
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5:16 - 5:17is the same thing as the light
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5:17 - 5:20that we can experience and study here on Earth.
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5:20 - 5:21So, since we know the physics
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5:21 - 5:22of how x-ray,
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5:22 - 5:23ultraviolet light,
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5:23 - 5:25or microwaves work here,
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5:25 - 5:28we can study the light of a distant star or galaxy
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5:28 - 5:30and know what kinds of things
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5:30 - 5:32are happening there too.
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5:32 - 5:33So, as you go about your daily life,
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5:33 - 5:36think beyond what your eyes can and can't see.
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5:36 - 5:38Knowing just a little bit about the natural world
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5:38 - 5:40can help you perceive the full spectrum
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5:40 - 5:42around you all the time.
- Title:
- Light waves, visible and invisible - Lucianne Walkowicz
- Speaker:
- Lucianne Walkowicz
- Description:
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View full lesson: http://ed.ted.com/lessons/light-waves-visible-and-invisible-lucianne-walkowicz
Each kind of light has a unique wavelength, but human eyes can only perceive a tiny slice of the full spectrum -- the very narrow range from red to violet. Microwaves, radio waves, x-rays and more are hiding, invisible, just beyond our perception. Lucianne Walkowicz shows us the waves we can't see.
Lesson by Lucianne Walkowicz, animation by Pew36 Animation Studios.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:58
TED edited English subtitles for Light waves, visible and invisible | ||
Jessica Ruby approved English subtitles for Light waves, visible and invisible | ||
Jessica Ruby accepted English subtitles for Light waves, visible and invisible | ||
Jessica Ruby edited English subtitles for Light waves, visible and invisible | ||
Jessica Ruby edited English subtitles for Light waves, visible and invisible | ||
Andrea McDonough edited English subtitles for Light waves, visible and invisible | ||
Andrea McDonough edited English subtitles for Light waves, visible and invisible |