Name: SPFの科学 - 日焼け止めはいかにしてあなたを安全に保つか! (The Science of SPF - How Sunscreen Keeps you Safe!)
Uploaded: 2021-01-14T08:51:11.000Z
Duration: 8 min 36 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：

付加疑問

Helps me make Vitamin D. And - incessantly bombards me with dangerous UV radiation.

The sun is both our friend, and our enemy.

You know the Sun makes visible light - it lights up everything we see!

But today, we’re talking about the light we CAN’T see.

There’s infrared - that makes up about half of the Sun’s energy that hits the earth.

Although it’s invisible, infrared radiation keeps us nice and cozy.

But that’s not what’s going to give you a sunburn or make you have wrinkles, or cause

About 8 percent of the Sun’s radiation is in this part of the spectrum.

UV light has a shorter wavelength than visible light.

MOST of the Sun’s radiation gets filtered out by our atmosphere, thank goodness.

This is one of the challenges of space travel, by the way - you want to be an astronaut,

you’re going to have to protect yourself against UV radiation - no more Earth’s cushy

Our ozone layer catches a good portion of UV.

But some of it still reaches us down here on the ground.

The peak hours for UV radiation are 10AM to 4PM.

Around 20% of UV radiation can be blocked on an overcast day.

Those rays are going to reflect right back at you.

All these factors will affect how much UV radiation reaches you.

The Ultraviolet Index is a rating scale, with numbers from 1 to 11.

The higher the UVI number, the more intense the UV rays you will be exposed to.The “daily

UVI” forecasts the amount of UV reaching your area at noon - when the sun typically

If you want to get into specifics, there are websites you can visit and apps you can download

to let you know what is your UV exposure on any given day, at your specific location.

For example, in the United States, The Environmental Protection Agency (EPA) offers UVI forecasts

by ZIP code on their UV Index page.You can even buy a little meter so you can make the

We’ll include links in the description below.

This is all to say - you need to take steps to protect yourself from UV radiation.

You can wear protective clothing - like this shirt I’m wearing was advertised as sun

The tighter the weave, the more protection your clothes will offer you.

Now keep in mind, the protection generally goes down when it gets wet.

Still, it’s not like I go around bundled up all the time.

I don’t know about you, but when it’s burning hot out, and I start shedding layers,

The effectiveness of sunscreen is measured in terms of FACTORS.

That’s what SPF stands for: sun protection FACTOR.

Your baseline determines how well the sunscreen will work for you, personally.

It’s not going to work exactly the same for you and all your friends, unless you just

randomly happen to have exactly the same amount of sun tolerance.

So let’s say you, PERSONALLY, can stay out in the sun for 15 minutes before you start

And you put on some sunscreen that is SPF 20.

Think of multiplying your personal tolerance by a FACTOR of 20.

15 minutes x 20 = 300 minutes, or 5 hours.

So this kind of sunscreen should, theoretically, protect you for up to 5 hours before you start

That means I can put on sunscreen and go out for 5 hours without thinking about it!

NO, no good, stop it, no wonder you’re a lobster!

They wear off, they rub off, they sweat off.

Most dermatologists recommend reapplying sunscreen every 2 hours.

But you should re-apply even sooner if you noticed you rubbed off on a towel, or washed

Most people don’t put on nearly enough sunscreen.

In fact, one study showed that it was best if you told people to put sunscreen on TWICE

- because then, they *might* put on enough sunscreen.

The general recommendation is 1 oz - about a shot glass full.

Don’t forget your ears, and the tops of your feet.

This man put sunscreen on one half of his face.

Then a photo was taken with UV light, so you can see just how much of the UV is absorbed

Everywhere UV is absorbed, his face is dark.

Now let’s take a closer look at the enemy.

UV can be broken down into 3 subclasses of radiation - UVA, UVB, and UVC.

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SPFの科学 - 日焼け止めはいかにしてあなたを安全に保つか! (The Science of SPF - How Sunscreen Keeps you Safe!)

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