Pictures that move through the air
Television sends moving pictures and sound from one place to screens everywhere. It shaped how people get news, watch sports, learn and are entertained. The word comes from Greek tele (far) and Latin visio (seeing): "seeing from afar."
How motion pictures trick your eyes
A TV doesn’t really show motion. It shows many still pictures very quickly, one after another. Your brain blends them into smooth movement. The number of pictures per second is the frame rate. TV in North America traditionally shows about 30 frames per second; movies use 24.
Inventing television
Television had many inventors.
| Year | Inventor | Achievement |
|---|---|---|
| 1884 | Paul Nipkow (Germany) | Spinning disc with holes to scan images line by line |
| 1897 | Karl Ferdinand Braun (Germany) | Cathode ray tube (CRT) |
| 1925–1926 | John Logie Baird (Scotland) | First mechanical TV to show recognizable moving faces |
| 1927 | Philo Farnsworth (USA) | First fully electronic TV system, at age 21 |
| 1920s–1930s | Vladimir Zworykin (Russian-American) | Electronic camera tube and picture tube |
| 1936 | BBC | First regular high-definition (for the time) TV service, in London |
Philo Farnsworth said he got the idea for scanning images in lines at age 14, while ploughing a potato field in rows.
How old CRT televisions worked
- A TV camera scanned the scene line by line, turning light into electrical signals.
- The signals were broadcast as radio waves from a tall antenna.
- The TV’s antenna received them.
- Inside the cathode ray tube, an electron gun fired a beam at the screen.
- Magnets steered the beam across the screen, line by line.
- Where the beam hit special chemicals (phosphors), they glowed, creating the picture.
Colour TVs had three electron beams, for red, green and blue.
Television in Canada
| Year | Event |
|---|---|
| 1952 | CBC begins TV broadcasting in Montreal and Toronto |
| 1958 | Microwave relay network links Canada from coast to coast |
| 1961 | CTV, Canada’s first private network, launches |
| 1966 | Colour TV broadcasts begin in Canada |
| 1972 | Anik A1 satellite brings TV to northern communities |
| 1981 | Inuit Broadcasting Corporation founded |
| 1999 | APTN (Aboriginal Peoples Television Network) launches, the first national Indigenous broadcaster in the world |
| 2011 | Over-the-air analog TV switches to digital in major markets |
Flat screens and digital TV
| Technology | How it works |
|---|---|
| LCD (liquid crystal display) | A backlight shines through liquid crystals that twist to block or let light through coloured filters |
| LED TV | An LCD screen lit by LEDs |
| OLED | Each pixel makes its own light; very thin with deep blacks |
| Plasma (older) | Tiny cells of gas glowed when charged |
Pixels and resolution
A screen image is made of tiny dots called pixels. Each pixel mixes red, green and blue light to make any colour.
| Resolution | Pixels |
|---|---|
| Standard definition | About 480 lines |
| HD (1080p) | 1920 × 1080, about 2 million pixels |
| 4K | 3840 × 2160, about 8 million pixels |
| 8K | 7680 × 4320, about 33 million pixels |
Ways to watch
| Method | How the signal arrives |
|---|---|
| Over-the-air broadcast | Radio waves to an antenna |
| Cable | Coaxial or fibre-optic cables |
| Satellite | Signals from satellites to a dish |
| Streaming | Over the internet to a TV, computer or phone |
Streaming services now let viewers watch what they want, whenever they want.
Impact of television
| Positive | Concerns |
|---|---|
| Shared national experiences, like the 1972 Summit Series and Moon landing | Too much screen time |
| News and live events from around the world | Advertising aimed at children |
| Educational shows like Sesame Street | Less physical activity |
| Entertainment and culture | Misinformation and violent content |
Common mistakes
- Thinking TV shows continuous motion. It shows rapid still frames.
- Thinking one person invented television.
Try it yourself
- Make a flipbook with 20 drawings. Flip it fast. How does it relate to frame rate?
- Look at a TV or phone screen with a magnifying glass. Can you see the red, green and blue pixels?
- Survey your family on how they watch TV: broadcast, cable, satellite or streaming.
Quick recap
- Television shows many still frames quickly to create motion.
- Inventors like Baird, Farnsworth and Zworykin developed TV in the 1920s.
- Old TVs used cathode ray tubes; modern TVs use LCD, LED and OLED pixels.
- CBC began Canadian TV in 1952; APTN launched in 1999.
- TV is delivered by broadcast, cable, satellite and streaming.