Above: Image © Berthold Werner, Wikimedia Commons

Glued to the tube? Most people are.

Every day, television provides viewers with millions of bite-sized electronic pieces of information about the weather, sports, this season's hottest fashion trends, and much more.

The term "television" (TV) (which is derived from Greek and Latin) literally means "far sight". This remarkable invention allows people to see things and places that don't necessarily have to be situated right in the middle of their living rooms.

In other words, TVs are rather convenient.

With the click of a button, people can tune in to their favourite shows. For those who wish to dust off some of those good, old-fashioned family values, there's Family Guy ; for those who would like to receive information about current world affairs, there's CNN, CTV, and perhaps, more appropriately, The Colbert Report ; and for those who wish to immerse themselves in drama (and, well, bore themselves out of their minds), there's Gossip Girl , for example.

But how exactly does all of this information get in and out of that little black box?

Prior to the 1990s, all TVs used cathode ray tubes— vacuum tubes that accelerate and deflect an electron beam towards a fluorescent screen— to produce pictures in the form of light.

All cathode ray tubes fire electrons from a heated cathode (an electrode that conducts positive electric current) inside an electron gun. The electrons emitted from the electron gun's heated cathode are accelerated towards the anode (an electrode that conducts negative electric current) via potential difference. When the electrons reach the fluorescent screen at the end of the hollow tube, they excite the atoms that coat the fluorescent screen. The excited atoms emit beams of radiation that are deflected towards their designated positions within the picture on the TV screen.

Did you know? Philo Farnsworth (at the tender age of fourteen) decided to use electron beams to "paint" pictures. Farnsworth's bright idea eventually led to the development of the first TV.

In a black-and-white TV, the fluorescent screen (which is lined with white phosphor) emits a beam of particles upon the viewing screen. Note that this beam of particles appears as a single dot upon the screen. This beam of particles is pushed side-to-side in a "raster scan" pattern over the viewing screen via magnetic coils. The particle beam rapidly paints horizontal lines of dots over the viewing screen, and each dot is processed to yield different shades of grey.

In other words, black-and-white TVs used different intensities of particle beams to create images composed of thousands of shaded dots.

Because these dots are so close together, the brain interprets these individual dots holistically, or as images. As an aside, TV images are unrecognizable at close range because the brain can't piece together the isolated dots.

Did you know? A TV screen typically contains about 480 horizontal lines of particle dots. These lines are retraced by the particle beams in specific patterns so as to "keep" the images on the screen.

Colour TVs work in ways similar to black-and-white TVs. However, there are three important differences:

Colour TVs use three different particle beams rather than one white particle beam. These three beams are called the red, green, and blue beams. Colour TVs use fluorescent screens that are coated with red, green, and blue phosphor rather than just white phosphor. The three kinds of phosphor are clumped together in specific patterns (usually lines) over the screen. There is a thin, perforated metal sheet called the "shadow mask" that lines the fluorescent screen of colour TVs. The holes within this metal sheet line up with the clumps of coloured phosphor.

After the 1990s, TVs received and transmitted digital rather than analog signals. Digital signals are easier to work with, as they code for discrete bits of information rather than long, continuous streams of information. Digital signals produce sharper images, and they also increase the number of available channels.

TVs are a physicist's dream. Grab a hollow glass tube, throw in an electron gun, an anode, some signal receivers and transmitters, a few electrical circuits, some phosphor, and— voila ! You've got yourself a primitive TV. But it is important to note that TVs (especially some of the newer models) are incredibly complicated in terms of their electrical wiring and overall set up.

So the next time you sit down, tune in—and tune out—to your favourite show, remember that there's more than meets the eye with a TV.

Learn More!

References:

Marisa Azad

Marisa is majoring in molecular genetics and microbiology at Thompson Rivers University and is currently working on a research project that is aimed towards making new antibiotics from scratch. Aside from being a self-confessed chocoholic and science junky, Marisa is a nationally-ranked athlete. She loves to watch action-packed movies and play with bacteria in her lab.


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Avatar  Matthew, and Nathan

We are 7th grade students in Zionsville West Middle School, we are looking for experts for how t.vs work for asking questions through out our project.