question_answer

Why do we require a satellite for long distance TV transmission? A fax message is to be sent from Delhi to Washington via a geostationary satellite. Calculate the minimum time delay between the dispatch and its getting received. (Take height of the geostationary satellite\[=\text{ }\mathbf{36},\mathbf{000}\text{ }\mathbf{km}\])    

Answer:

                TV signals being of high frequency range, 100-220 MHz, cannot be reflected by ionosphere. Also ground wave transmission is possible only up to a limited range. That is why satellites are used for long distance TV transmission. The transponders in a satellite receive these signals and transmit them towards different ground stations. Numerical: Minimum distance, \[\text{s }=2h=\text{ 2 }\times \text{ 36}000\text{ km}\] \[=\text{ 72}000\text{ km}\]