Standard Grade Physics Notes

TELECOMMUNICATIONS
SUMMARY NOTES
SECTION DESCRIPTION of CONTENTS 1. Communication using waves 2. Communication using cables Speed of sound. Waves. Communication with wires between transmitter and receiver. Telephone. Electrical signals in the communicating wires. Optical fibre communications. Fibres vs Electrical cables. Laws of reflection. Signal transmission. Receiver, aerial, tuner, decoder, amplifier. Television: Receiver, aerial, tuner, decoders, amplifiers, picture tube, black and white picture, colour picture. Transmission and reception Waves, wavelength, frequency band. Dish aerials, curved reflectors. Satellites. Geostationary satellites and ground stations. Radio:

3. Radio and Television

4. Transmission of Radio waves

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Section 1: SPEED OF SOUND

340m/s
contains microsecond timer
COMPUTER

Sound operated switch

INTERFACE

Sound operated switch

1 metre

Stick and bottle

Measuring the speed of sound waves in air. The apparatus used is shown above. The distance between the two sound operated switches is measured using a metre stick and entered in the computer programme. A sharp sound is produced by the stick hitting the bottle. When the sound reaches the first sound operated switch, it turns on the timer in the computer. When it reaches the second sound operated switch, the timer is turned off. The speed of sound is calculated from: speed of sound = distance between the sound switches time taken

Sound travels at 340 m/s in air. Light travels at 300,000,000 m/s in air. During thunder storms we see the flash of lightning before we hear the thunder,

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Section1: THE WAVE EQUATION Direction of travel Crest Amplitude
Line of zero disturbance

Wavelength l

l Wavelength

Trough

DEFINITIONS Wavelength(λ) The wavelength of a wave is the distance between two successive l peaks, or two successive troughs. Wavelength is measured in metres. Frequency(f) The frequency of a wave is the number of waves produced...