Light waves, visible and invisible

Ondas de luz, visible e invisible - Lucianne Walkowicz

Translator: Lúa Cruz Fernández Reviewer: Serv. de Norm. Lingüística U. de Santiago de Compostela

What if you could only see one color?

Que pasaría se só puideses ver unha cor?

Imagine, for instance,

Por exemplo, imaxina

that you could only see things that were red

que só puideses ver as cousas de cor vermella

and that everything else

e que todo o demais

was completely invisible to you.

fose totalmente invisible.

As it turns out,

En realidade,

that's how you live your life all the time

así é como viviches todo este tempo

because your eyes can only see

porque só podes ver

a minuscule part of the full spectrum of light.

unha pequena parte do espectro completo de luz.

Different kinds of light are all around you everyday

Todos os días hai diferentes tipos de luz arredor túa

but are invisible to the human eye,

que son invisibles para o ollo humano,

from the radio waves that carry your favorite songs,

dende as ondas de radio coas túas cancións favoritas,

to the x-rays doctors use to see inside of you,

até os raios X que os médicos usan para verte por dentro,

to the microwaves that heat up your food.

ou as microondas que quentan a túa comida.

In order to understand

Para entender

how these can all be light,

como todo isto poder ser luz,

we'll need to know a thing or two

debemos saber un par de cousas

about what light is.

sobre ela.

Light is electromagnetic radiation

A luz é unha radiación electromagnética

that acts like both a wave and a particle.

que actúa como unha onda e unha partícula.

Light waves are kind of like waves on the ocean.

As ondas de luz son coma as do océano.

There are big waves and small waves,

Hainas grandes e pequenas,

waves that crash on the shore

ondas que chocan na beira,

one right after the other,

unha após outra,

and waves that only roll in every so often.

e ondas que chegan menos a miúdo.

The size of a wave is called its wavelength,

Ao tamaño dunha onda chámaselle "lonxitude de onda"

and how often it comes by

e á regularidade con que chega,

is called its frequency.

"frecuencia".

Imagine being a boat in that ocean,

Imaxina que estás nun bote no océano,

bobbing up and down as the waves go by.

mentras abaneas ao ritmo da ondada.

If the waves that day have long wavelengths,

Se as ondas dese día teñen teñen moita lonxitude,

they'll make you bob only so often,

abanearás lentamente,

or at a low frequency.

ou cunha frecuencia baixa.

If the waves, instead, have short wavelengths,

Pero se teñen pouca lonxitude,

they'll be close together,

se veñen moi seguidas,

and you'll bob up and down much more often,

abanearás máis á présa,

at a high frequency.

é dicir, cunha frecuencia alta.

Different kinds of light are all waves,

Todas as ondas son distintos tipos de luz,

they just have different wavelengths and frequencies.

só que teñen diferentes lonxitudes de onda e frecuencias.

If you know the wavelength or frequency

Se sabes a lonxitude ou a frecuencia

of a wave of light,

dunha onda de luz,

you can also figure out its energy.

tamén podes calcular a súa enerxía.

Long wavelengths have low energies,

Unha lonxitude de onda longa ten baixa enerxía,

while short wavelengths have high energies.

e unha lonxitude curta tena alta.

It's easy to remember

É facil de lembrarse

if you think about being in that boat.

se volves a imaxinarte nun barco.

If you were out sailing on a day

Se navegas nun día

with short, choppy waves,

con ondas curtas e picadas,

you'd probably be pretty high energy yourself,

de seguro has ter que empregar moita enerxía

running around to keep things from falling over.

para correr e termar das cousas para que non caian.

But on a long wavelength sea,

Nun mar de ondas longas,

you'd be rolling along, relaxed,

navegarás tranquilamente,

low energy.

con pouca enerxía.

The energy of light tells us

A enerxía da luz dinos

how it will interact with matter,

como vai interactuar coa materia,

for example, the cells of our eyes.

por exemplo, coas células dos ollos.

When we see, it's because the energy of light

Cando vemos é porque a enerxía da luz

stimulates a receptor in our eye

estimula un receptor no noso ollo

called the retina.

chamado "retina".

Our retina are only sensitive to light

A nosa retina só é sensible á luz

with a very small range in energy,

dun rango de enerxía moi pequeno,

and so we call that range of light visible light.

ao que lle chamamos "luz visible".

Inside our retina are special receptors

Dentro da retina temos receptores especiales

called rods and cones.

chamados bastón e conos.

The rods measure brightness,

Os bastóns miden a luminosidade,

so we know how much light there is.

de modo que sabemos canta luz hai.

The cones are in charge of what color of light we see

Os conos encárganse da cor da luz que percibimos.

because different cones are sensitive

Os distintos conos son sensibles

to different energies of light.

a distintas enerxías da luz.

Some cones are more excited by light

Algúns actívanse coa luz

that is long wavelength and low energy,

de lonxitude de onda longa e baixa enerxía

and other cones are more excited

e outros actívanse

by short wavelength, high-energy light.

coa de lonxitude de onda curta e alta enerxía.

When light hits our eye,

Cando a luz chega ao ollo

the relative amount of energy each cone measures

a cantidade relativa de enerxía que mide cada cono

signals our brain to perceive colors.

envíalle un sinal ao cerebro para que perciba unha cor.

The rainbow we perceive

Cando vemos o arco da vella

is actually visible light in order of its energy.

en realidade é luz visible segundo a súa enerxía.

At one side of the rainbow

Nun lado,

is low-energy light we see as red,

está a luz de baixa enerxía, que vemos como vermella,

and at the other side is high-energy light

e no outro, a de alta enerxía,

we see as blue.

que vemos como azul.

If light shines on us

Se a luz que brilla sobre nós

that has an energy our retina can't measure,

ten unha enerxía que a retina non pode medir

we won't be able to see it.

non imos poder percibila.

Light that is too short wavelength or high energy

A superficie do ollo absorbe a luz con

gets absorbed by the eye's surface

lonxitude de onda moi curta ou alta enerxía

before it can even get to the retina,

antes incluso de que chegue á retina

and light that is too long wavelength

e a luz cunha lonxitude de onda moi longa non ten enerxía abonda

doesn't have enough energy

to stimulate our retina at all.

para estimular a retina.

The only thing that makes one kind of light

O único que fai que un tipo de luz

different from another is its wavelength.

sexa diferente doutro é a lonxitude de onda.

Radio waves have long wavelengths,

As ondas de radio teñen unha lonxitude

while x-rays have short wavelengths.

de onda longa, os raios X curta.

And visible light, the kind you can actually see,

E a luz visible, a que podes percibir en realidade,

is somewhere in between.

atópase no medio.

Even though our eyes can't detect light

Aínda que os ollos non poden detectar a luz

outside of the visible range,

que está fóra do rango visible,

we can build special detectors

podemos crear detectores especiais

that are stimulated

estimulados por luces

by these other wavelengths of light,

con esoutras lonxitudes de onda,

kind of like digital eyes.

como se fosen ollos dixitais.

With these devices,

Con estes aparellos

we can measure the light that is there,

podemos medir a luz que está aí

even though we can't see it ourselves.

aínda que non a poidamos ver.

So, take a step back and think about

Entón, para un segundo

all of this for a moment.

e pensa en todo isto un momento.

Even though they seem different,

Aínda que parecen distintas,

the warmth you feel from a crackling fire

a calor dunha lumarada

is the same as the sun shining on you

é igual ca a do sol brillando

on a beautiful day,

nun fermoso día,

the same as ultraviolet light

igual ca a da luz ultravioleta

you put on sunscreen to protect yourself from,

da que te protexes con crema solar,

the same thing as your TV,

ou ca a da túa televisión,

your radio,

a túa radio

and your microwave.

ou o teu microondas.

Now, those examples are all things here on Earth,

Todos estes exemplos danse na Terra,

things you experience in your everyday life,

son cousas da vida cotiá,

but here's something even more amazing.

máis hai algo aínda máis asombroso.

Our universe gives off the full spectrum of light, too.

O noso universo tamén emite o espectro completo da luz.

When you think of the night sky,

Cando pensas no ceo nocturno,

you probably think of being able

probablemente supós que podes

to see the stars shining with your own eyes,

ver as estrelas brillar cos teus propios ollos,

but that's just visible light,

máis iso é só a luz visible,

which you now know is only a tiny part

que xa sabes que é só unha pequena parte

of the full spectrum.

do espectro completo.

If we had to draw the universe

Se debuxásemos o universo

and could only use visible light,

e só puidésemos empregar a luz visible,

it would be like having only one crayon --

sería como ter un só lápiz de cores

pretty sad.

--bastante triste.

To see the universe in its full spectrum,

Para ver o universo co seu espectro completo

we need to have the right eyes,

necesitamos os ollos adecuados,

and that means using special telescopes

o que significa usar telescopios especiais

that can help us see beyond visible light.

que nos axuden a ver máis alá da luz visible.

You've probably heard of the Hubble Space Telescope

Seguro que oíches falar do Telescopio Espacial Hubble

and seen its beautiful pictures

e viches as incribles fotos

taken in visible and ultraviolet light.

que tirou con luz visible e utravioleta.

But you might not know

Máis talvez non saibas

that there are 20 space telescopes in orbit,

que hai 20 telescopios espaciais en órbita

missions that can each see part

en misións en que cada un ve

of the full spectrum of light.

parte do espectro completo de luz.

With telescopes acting as our virtual eyes,

Cos telescopios actuando coma ollos virtuais,

both in space and here on Earth,

tanto no espazo coma na Terra,

we can see some amazing things.

podemos percibir cousas asombrosas.

And the coolest thing of all,

E o mellor de todo,

no matter the wavelength or energy,

sen que importe a lonxitude de onda ou a enerxía,

the light that we see out in the distant universe

a luz que percibimos no afastado universo

is the same thing as the light

é igual ca a luz

that we can experience and study here on Earth.

que percibimos e estudamos na Terra.

So, since we know the physics

Ao coñecer a física

of how x-ray,

de como os raios X,

ultraviolet light,

a luz ultravioleta

or microwaves work here,

ou as microondas funcionan aquí,

we can study the light of a distant star or galaxy

podemos estudar a luz dunha estrela ou galaxia afastada

and know what kinds of things

e descubrir que cousas

are happening there too.

ocorren alí tamén.

So, as you go about your daily life,

Entón, no teu día a día

think beyond what your eyes can and can't see.

pensa alén do que poden ver os teus ollos.

Knowing just a little bit about the natural world

Se aprendemos un chisco do noso mundo natural

can help you perceive the full spectrum

poderemos percibir mellor todo o panorama

around you all the time.

que se atopa arredor noso todo o tempo.