동영상강좌
  CF로 배우는영어
  생활속표현
  영어뉴스
  오디오*비디오 수업
  오늘의 동영상
  강사가 들려주는 금주의 명언
홈 > 커뮤니티 > 오늘의 동영상   
 
The Science of Rainbows
관리자 2020-05-26 오후 2:06:16 819

 

Description: 

Our culture, and our skies, are full of rainbows, but do you know how they form? 

Do we all see the same rainbow? Could cyborg-enhanced mantis shrimp eyes 

someday see a bigger rainbow? 

 

Transcription: 

From coloring books to record covers, rainbows are everywhere.

I bet you can even remember the colors without thinking twice. 

Although in real life no one really says "indigo", although I guess ROYGBV 

doesn't really have the same ring to it. As anyone who's tried to chase 

one finds out, a rainbow isn't really there. 

You can't go over it, and you can't get to the end of it. It's become 

a mythical representation of the unattainable.

In Navajo and Norwegian mythology, it's a bridge that only gods could take

between heaven and Earth. 

For Christians and Buddhists, rainbows are a state of peace and forgiveness.

And in some cultures, it's a really long and colorful unicorn.Of course,

just because a rainbow isn't really there doesn't mean we can't explain

how it works. The better question is "WHY is a rainbow?

" And that answer is "42"Let me explain. A rainbow exists because of light, 

water and a little physics.Let's start with sunlight. It looks white. 

To some that seems like the absence of color.

But thanks to Isaac Newton we know that white light is really the sum of all visible 

wavelengths, from short to long and all the colors in between. 

So we've got light,now we need water. On a rainy or misty day, 

the sky is filled with tiny droplets.They aren't quite as small as the droplets

in clouds, though, which is why we don't have awesome looking clouds. 

Some of you might be saying "But Joe, 

I've seen a rainbow in a cloud before! Well, that's not really a rainbow. 

But we'll talk about that another time. 

Those suspended liquid prisms are surface tension on its smallest scale, 

and they're pulled into the shape of a sphere and each one can catch sunlight 

and become its own part of the rainbow factory. 

Here's where we add the physics. Sunlight starts by entering a raindrop from

behind you. The light goes from one medium, air, into another, water.

And that causes it to bend slightly thanks to a process called refraction.

Different wavelengths of light bend at different angles so the white light begins

to separate. This bent sunlight then reflects off the back of the raindrop,

and refracts again on the way out. When we measure the angle between 

the light that went in and the red light that comes out, the answer is 42 . . . 

degrees. So how many drops does it TAKE to make a rainbow? Well, a lot. 

Because each color exits at a different angle, one raindrop will send red light 

into your eye and another drop will send violet light. The same thing happens

with all the colors in between, each coming from their own droplet.

And what about the shape? We call it a rainBOW for a reason.

It's not a rainLINE or a rainZIGZAG. You and your eyes are at the apex of a huge

half-cone, and at the other end is the water that makes the rainbow shape that

we all know and love. Everything that you see is because that light is refracting

right to where you are. No one else is experiencing exactly the rainbow as you. 

If everyone's rainbow is unique, does your rainbow look like my rainbow? Well,

Michael from Vsauce has a great video about that, so I'll put a link in the description

to let him answer that question for you.

Could we ever see a different rainbow?

We've evolved to see only a tiny fraction of a percent of the entire electromagnetic

spectrum, what about all the rest of it, from x-rays to radio waves. What if we could

see a rainbow like the mantis shrimp, maybe we could see a rainbow that stretches 

across the sky! Spoiler alert, maybe NOT. 

While it's true that we only see a sliver of the spectrum, you can't make a rainbow 

out of anything that doesn't make it into Earth's atmosphere. 

Take the sun: It actually emits almost half of its radiation

right around the visibla range, which is exactly why we evolved to see that range.

The rest of the sunlight is mostly infrared and just a tiny bit of UV. If we could see 

a rainbow made of all of that, it would only be about twice the width of the one

we're used to. Unfortunately, if we could see infrared, 

we'd be blinded by the infrared radiation given off by all the warm 

things around is,including the Earth itself.Cranking up the sun wouldn't 

work either because most of the electromagnetic spectrum is filtered out 

before it reaches Earth's surface. What about all those radio waves, 

they're traveling freely through the atmosphere. Picture all those bands 

way beyond the red side of our rainbow. Sadly, having radio antennas 

for eyes would also be a blinding experience, because the air is filled with 

the signals from our wi-fi, mobile phones,and well, radio. I guess we'll have 

to be happy with the rainbow we have,because it's pretty much the best 

rainbow we can make.The next time you see a rainbow,

remember that even though there's no pot of gold at the end, no one else 

can see exactly same rainbow you can. That sounds like treasure to me. 

 

Questions: 

1. How many colors of the rainbow? Enumerate the colors. 

2. Specify the significance of rainbow in some culture and religion. 

3. Explain the components of a rainbow.


첨부파일 Uploaded File : 2020052614614_2UU8I.jpg  
The Cosmic Calendar | Cosmos: Possible Worlds
What would happen if you didn’t drink water?