Waves and Technology | Information Technology | High School Physics | Khan Academy

- [Narrator] We've already
learned a lot about waves

and now we're going to connected
to the bit to technology,

especially the technology that most of us

use most frequently and
that's our cell phone.

So pause this video and
think if you can list

all of the waves that your cell phone

has to utilize or deal
with or generate waves.

All right, so the first
thing that some of you

might have realized is
that your cell phone

has to deal with sound waves.

So you have sound
traveling through the air.

Your phone has to detect that sound.

And then in most cases, it
needs to digitize that sound.

And we did other videos
where we talked about

sampling sound waves so
that you can store it

as digital information.

And then depending what's happening,

that detection is going to
happen with your microphone.

And if you were recording something,

say recording a video or
recording an audio file

that digitize sound wave
would then be stored.

And then if you wanted to play it back,

it would have to be turned
back into a sound wave,

which could then be
emitted by your microphone.

Now, it could also be that you're on,

let's say a video call or you are having

an actual phone call, the
original purpose of phones.

And so then that digitized information

is going to be transmitted to a cell tower

that could be tens of miles away.

And I always find that
amazing because the cell phone

really has, it doesn't transmit
in a particular direction,

it kind of transmits in every direction.

So it's got to be pretty powerful
to get to that cell tower

that might be around five or
10 or even more miles away.

And then of course, if
you're having a conversation,

that cell tower is transmitting
electromagnetic waves

in a bunch of different directions.

And then this cell phone says,

"Hey, that's the signal for me."

And it can take that digital information.

And then it could use that
to generate a wave pattern,

which is then emitted
by the microphone again,

which you'd then hear.

So sound waves is clearly a
big part of what's going on

with a lot of technology, not
just cell phones, obviously.

If you have a stereo system,
if you have a television,

sound waves are heavily utilized,

or at least you have to deal with them.

Now, what other type of wave?

Well, you might be saying light waves,

which would be correct,

but I'm gonna generalize
a little bit more and say,

electromagnetic waves of which light waves

are a type of electromagnetic waves.

How do you use light waves?

Well, a modern smartphone or
cell phone will have a camera.

And so it needs a way
to detect light waves.

So it will detect them and
once again, it will digitize,

it will store and then of course,

it has this nice big screen here.

So it needs a way to take
that digitized information

and then generate light waves.

Every pixel on the screen can
generate different frequencies

of light waves or at least
give the appearance altogether

of generating different
frequencies of light waves.

Now, light waves are not the only type

of electromagnetic wave.

We've talked about having to
communicate with a cell tower

that could be 5, 10, 15,
even further miles away.

Well, those waves it's using to connect

with your cell tower,
those are radio waves,

which are another type
of electromagnetic waves.

Now, are we done?

Well just to make sure we can
look at this little key here

that you see at the top of a cell phone,

and you could see that
cell signal that tells you

how good of a radio signal it is getting

from the cell tower,

but you can also see
this Wi-Fi signal here.

So Wi-Fi uses different
frequencies of radio waves

to communicate with the local
network wherever you are.

But once again, that is more radio waves.

So I will let you go.

I encourage you as you
learn anything in any topic.

Always look at the world around you

and see how these concepts
that you're learning in school

or that you're learning
in, say a Physics class

are connected to things you
do every moment of your life.