# Telecommunications

 In air, the speed of sound is....? 340 m/s In air, the speed of light is...? 3 x 108 m/s What is the formula for speed-distance-time? d=vt What is the wave equation? v=f λ What is another equation you can use to work out the frequency of a wave? f = n ÷ t What is the amplitude of a wave? The distance from the zero line to the crest or the trough What is the wavelength of a wave? The distance from any point on a wave to the point where it starts to repeat. What is the speed of light in optical fibres? 2 x 108 m/s Name and describe the parts of a radio Ariel - picks up many signals Tuner - selects one frequencyDecoder - gets the audio signal back from the modulated wavePower supply - supplies energy to the amplifierAmplifier - makes the audio signal strongerSpeaker - changes electrical signal into sound What is amplitude modulation? 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 Explain "Line Build Up" 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. Explain "Image Retention" 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. Explain why we see a moving image on TV 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. To increase the brightness of a television picture _____ electrons are fired at the screen every second? more To decrease the brightness of a television screen _____ electrons are fired at the screen every second? less Name the parts of a television ArielTunerAudio and visual decoderAudio and visual amplifier Power supplySpeakerTelevision tube What are the three main colours on a TV screen? RedBlueGreen How do you make yellow? Red and Green light How do you make magenta? Blue and Red light How do you make cyan? Green and Blue light How do you make black / white light? Black - light up no dotsWhite - Blue, Red and Green light What does fitting a curved reflector dish to a reciever ariel do to the signal and why? It makes the signal stronger because it collects all of the signal and reflects it all to the ariel. What is meant by a Geostationary Satellite? 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. What is diffraction? The bending of a wave around an obstacle Long waves diffract ______ than short waves? more What are the advantages of optical fibres over copper cables? There is little loss of energy due to the pure glassFewer repeater units are neededThey are free from electrical interferenceMuch lighter than copper cablesThey cost lessThey carry more signals AuthorAnonymous ID62751 Card SetTelecommunications DescriptionStandard Grade Physics - Telecommunications Updated2011-01-29T17:11:26Z Show Answers