Name: 光の紹介 (Introduction to Light)
Uploaded: 2021-01-14T05:09:56.000Z
Duration: 9 min 37 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

再帰代名詞

What I want to do in this video is give ourselves

a basic introduction to the phenomenon of light.

And light is, at least to me, mysterious.

Because on one level it really defines our reality.

It's maybe the most defining characteristic of our reality.

Everything we see, how we perceive reality,

is based on light bouncing off of objects

or bending around objects or diffracting around objects,

and then sending signals into our brain that

create models of the world we see around us.

So it really is, almost, the defining characteristic

But at the same time, when you really go down to experiment

to have a bunch of mysterious properties.

And to a large degree it is not fully understood yet.

And probably the most amazing thing about light--

well, actually there's tons of amazing things about light--

but one of the mysterious things is when you really get down

to it-- and this is actually not just true of light,

once you get onto a small enough quantum mechanical level--

light behaves as both a wave and a particle.

And this is probably not that intuitive to you,

In my life, I'm used to certain things behaving as waves,

like sound waves or the waves of an ocean.

And I'm used to certain things behaving like particles,

like basketballs or-- I don't know-- my coffee cup.

And it really depends on what experiment you run

with the photoelectric effect-- and I won't go into the details

we start thinking about quantum mechanics--

you can view light as a train of particles moving

at the speed of light, which I'll talk about in a second.

If you view light in other ways-- and you see it

even when you see light being refracted by a prism here--

It has a frequency, and it has a wavelength.

And like other waves, the velocity of that wave

Now even if you ignore this particle aspect of light,

if you just look at the wave aspect of the light,

Because most waves require a medium to travel through.

So for example, if I think about how sound travels through air--

I'll draw a sound wave traveling through the air particles.

What happens in a sound wave is you compress some of the air

particles and those compress the ones next to them.

And so you have points in the air that have higher,

High pressure, low pressure, high pressure, low pressure.

And as these things bump into each other,

and this wave essentially travels to the right--

and if you were to plot that you would see this wave

But this is all predicated, or this is all

based on, this energy traveling through a medium.

And I'm used to visualizing waves in that way.

Light will actually travel fastest through nothing,

And it will travel at an unimaginably fast speed--

3 times 10 to the eighth meters per second.

Or another way of thinking about it is it

would take light less than a seventh of a second

Or it would travel around the earth more than seven times

And not only is this just a super fast speed,

is something fundamental to our universe.

Because it's not just an unimaginable fast speed.

It is the fastest speed not just known to physics, but possible

So once again something very unintuitive to us

is going at some speed, maybe if there was an ant riding on top

of that something and it was moving in the same direction,

But nothing can go faster than the speed of light.

It's absolutely impossible based on our current understanding