Contents
Independent final check
Explain without the key
explain / identify / predict
Final check
(a) An engineer on shore steers a robot arm on an oil platform far out at sea, through a satellite link. She must see each move less than 0.1 s after she gives the command. Explain why a link through a geostationary satellite cannot do this, and identify the kind of satellite that can. (b) A designer suggests a satellite that goes round the Earth once a day, but in an orbit that passes over both poles. Predict whether a dish fixed to a roof could point at it all the time, and explain your prediction. (c) Supplement. In a hotel, guests use the wi-fi in a gym in the basement, two floors below the router. Films for up to 300 guests at once come from the town, 20 km away, along a cable under the road. For each, identify the region of the electromagnetic spectrum used, and explain why it suits the job.
explain: give reasons and connect them to evidence. identify: name or select. predict: use the information to say what you expect.
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Scope and sources
Cambridge IGCSE Physics 0625 · 2026–2028 v2 · Original learning materials.
Communication with artificial satellites, mainly by microwaves: low-orbit satellites for some satellite phones, geostationary satellites for other satellite phones and for direct broadcast satellite television (3.3.5); Supplement: why mobile phones and wireless internet use microwaves, Bluetooth radio waves, and optical fibres visible light or infrared (3.3.7); digital and analogue signals (3.3.8); a sound sent as a digital or analogue signal (3.3.9); the benefits of digital signals, a higher rate of data and a greater range through accurate regeneration (3.3.10). The regions of the electromagnetic spectrum and their other uses are in Light and the electromagnetic spectrum; total internal reflection in optical fibres is in Refraction; orbits and their periods are in the Space physics modules; how a signal is put onto a carrier wave and how a sound is sampled are not covered.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus