JOAN CARTAN-HANSEN, HOST: Television uses electromagnetic energy to bring pictures and sound into your house.

But you can only watch television because of the special way your brain deals with images.

(Music) KID ONE: What are you doing?

KID TWO: Trying to figure out why the TV isn't working.

CARTAN-HANSEN: I can help you understand how television works.

KIDS: Whoa!

CARTAN-HANSEN: Before we talk about how television works you have to understand how your brain processes images.

And it starts with dots.

If you divide an image into a collection of small dots, your brain can reassemble the dots into something that makes sense.

If you are too close, the dots look like, well, a blob.

But if you get far enough back, or if the dots get smaller, the image takes shape.

Television and computer screens use thousands of dots fused together to make images.

These dots are called pixels.

The other way your brain processes pictures is if you take a series of still pictures and move them in rapid succession, your brain interprets the image change as movement.

A flip book, animation, movies, and television are all individual frames moving in succession.

The images need to move at least 15 frames per second for the brain to process movement.

Film is shot at 24 frames per second and television is shot at about 30 frames per second.

Okay, now you understand how your brain processes images.

So let's talk about how television was developed.

A lot of people had a hand in developing television but one of the most important inventors came from Idaho.

When he was 14, Philo T. Farnsworth got the idea of creating television pictures by dividing pictures into a series of rows.

The idea came to him when he was plowing a field.

In 1927, he invented a vacuum tube and called it an image dissector or an early television camera.

It could change a picture into a radio signal.

Vladimir Zworykin invented a picture tube called a kinescope.

It was an early television receiver.

It could change radio signals back into pictures.

Television started out using an analog system.

Analog is the process of taking an audio or video signal and translating it into electronic pulses.

You can recognize an analog television because, in most cases, it uses at least one large vacuum tube.

It's probably that large tube that sticks out the back, giving analog TVs that odd shape.

Today, we basically use digital television.

In digital television, the audio and video information is broken up into a series of ones and zeros and that digital stream is sent out as a broadcast signal.

Television and radio signals are a part of the electromagnetic spectrum just like light waves.

KID ONE: But how does the picture get from the studio to my TV?

CARTAN-HANSEN: It's complicated, but here's the basic process.

Say I'm standing before a camera.

Light waves go through the lens and into a device that is kind of like a prism.

It splits the light into a stream of red, green, and blue.

Special sensors pick up each different stream and that information is processed into a digital signal.

At the same time, sound waves go into a microphone and are captured by an audio sensor and processed as digital information.

The audio and light data are combined and sent as a digital signal to the station's transmitter.

The transmitter increases the strength of the signal and broadcasts it over the air to homes everywhere.

That digital signal can also be delivered to homes using satellites, through a cable or via the internet.

Once the signal gets to your television or receiver, it's separated.

The audio part of the digital signal goes to the audio processor and out the speaker.

The visual part of the digital signal is processed into thousands of individual dots or pixels.

Now, there're a number of different kinds of digital televisions, but one of the most common is an LED flat screen.

An LED television has thousands of individual light-emitting diodes or L-E-D's.

The video processor sends the data, line by line, across the screen, telling each individual led what color it should show and how bright it should be.

All those tiny L-E-Ds or pixels, together, make up the picture.

The overall picture with those individual pixels changes about 30 times a second.

Light and sound waves emit from the television, where your ears and eyes pick them up and your brain puts it all together.

KID TWO: And we see it as television.

CARTAN-HANSEN: Right.

Now this is a simplified explanation.

There is a lot to the science of television.

But whether you watch it on your TV or watch it on another device, the process is basically the same.

KID ONE: But Idaho Public Television is always broadcasting a signal, why didn't our TV pick it up?

CARTAN-HANSEN: Oh, I figured that out.

You forgot to plug it in.

KIDS: Oh.

CARTAN-HANSEN: If you want to learn more about Television check out the Science Trek website.

You'll find it at Science Trek dot org.

(Music) ANNOUNCER: Presentation of Science Trek on Idaho Public Television is made possible through the generous support of the Laura Moore Cunningham Foundation, committed to fulfilling the Moore and Bettis family legacy of building the great state of Idaho, by the Idaho National Laboratory, mentoring talent and finding solutions for energy and security challenges; By the Friends of Idaho Public Television and by the Corporation for Public Broadcasting.