Telecommunications

340 m/s

3 x 10⁸ m/s

d=vt

v=f λ

f = n ÷ t

The distance from the zero line to the crest or the trough

The distance from any point on a wave to the point where it starts to repeat.

2 x 10⁸ m/s

• Ariel - picks up many signals
• Tuner - selects one frequency
• Decoder - gets the audio signal back from the modulated wave
• Power supply - supplies energy to the amplifier
• Amplifier - makes the audio signal stronger
• Speaker - changes electrical signal into sound

At a radio station, a low frequency audio wave is combined with a very high frequency radio wave called a carrier wave. The amplitude of the radio changes (modulates) a process called amplitude modulation

• The inside of a television screen is coated with a large number of phosphor dots, arranged in many lines.
• When electrons hit the phosphor dots, the dots give out light for a fraction of a second.
• An electron beam is moved across the screen, one line at a time. This happens 25 times every second. This process is known as line build up.

• There are 25 different pictures on a TV screen every second.
• The human eye/brain system holds on to the image for a fraction of a second before replacing it with another image - this is known as image retention.

As the pictures on a television screen are changing so quickly, the eye/brain system cannot detect them changing. It blends successive particles together, so we see a moving picture.

more

less

• Ariel
• Tuner
• Audio and visual decoder
• Audio and visual amplifier
• Power supply
• Speaker
• Television tube

• Red
• Blue
• Green

Red and Green light

Blue and Red light

Green and Blue light

• Black - light up no dots
• White - Blue, Red and Green light

It makes the signal stronger because it collects all of the signal and reflects it all to the ariel.

• A satellite that appears to be stationary above the earth as the earth spins.
• The period of the satellite will be 24 hours - the same period as the earth takes to rotate.

The bending of a wave around an obstacle

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• There is little loss of energy due to the pure glass
• Fewer repeater units are needed
• They are free from electrical interference
• Much lighter than copper cables
• They cost less
• They carry more signals