Nhóm Nguyễn Bá Duy Nguyễn Khắc Ngân Trần Minh Đức Vũ Văn Chinh Dương Văn Hùng Đỗ Văn Sang Task 1: Television x-rays machine microwave oven telephone aerial Task 2: Surface wave Frequencies low Frequencies Travels along the ground, flowing the curvature of the earth’s surface Range the range is about 1500km at low Frequencies Difficulties Task 3: energy is absorbed from it by the ground Sky wave Space wave Frequencies High frequencies Very high or ultra high frequencies Travels Bounces back to the ionosphere where it is again gradually refracted and return earthwards Giving line of sight transmission Range Around the earth if it enough energy A range of up to 150km is possible on earth Difficulties the critical frequency varies with the time of day and the seasons can be hampered by hills, tall buildings, trees Task 4: 1-a transmitting aerial 2-e surface wave 3-d space wave 4-c sky wave 5-b receiving aerial Task When the switch is closed ,current flows through the primary of the transformer When the radar signal strikes a plane It is reflected on discharging quickly, a cell may become hot When the TV receives signals from the remote control, it follows your instructions When the radar receiver receives the reflected signal, the signal is compared with the transmitted signal On choosing a course in electronics, you think carefully about your future When microwave signals strike a high building, they are deflected On making a recording, you should ensure the recording levels are satisfactory On detecting an intruder, the alarm triggers an audible warning 10 When the remote control button is pressed , the television set changes channel Task 7: verb absorb attenuate communicate conduct induct modulate reflect resist Noun (component) absorbent attenuator communicator conductor inductor modulator reflector resistor Task 9: AF - audio frequency RF - radio frequency AM – amplitude modulated Noun (property) absorption attenuation communication conductivity induction modulation reflection resistance FM – frequency modulated Task 10: FM carrier - d AM carrier - c AF signal - b RF carrier - a Task 11: aerial Receives weak RF signals RF tuner tuned to the required radio frequency and selected RF waves passed on to the RF amplifier RF amplifier convert a low-power radiofrequency signal into a larger signal of significant power detector recovers information contained in a modulated radio wave AF amplifier amplifies low-power audio signals to a level suitable for driving loudspeakers 6 loudspeaker Converts the audio signal into sound