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| Questão | Responda |
| P1g - Wireless Signals | Electromagnetic radiation can be used for wireless communications. For example: - radio waves are used to transmit television and radio programmes - microwaves are used to transmit mobile phone calls. |
| Interference | Radio stations whose transmitters are near each other need to broadcast on different frequencies to avoid interference between the signals. |
| DAB Vs FM | DAB - Digital Audio Broadcasting - is a digital system for transmitting radio programmes. FM, Frequency Modulation, is an analogue system for transmitting radio programmes. Both have advantages and disadvantages. For example: DAB makes more radio stations available and suffers from less interference from other broadcasts. On the other hand, DAB may have a poorer audio quality than FM, and not all areas of the UK are currently covered by DAB broadcasts. |
| Refraction | Radio waves are refracted by different layers in the Earth’s atmosphere. This leads to a reduction in the signal, making it difficult for them to be received over long distances. Unlike radio waves, microwaves are not refracted, so they are used for satellite communications. |
| Diffraction | Radio waves are diffracted when they meet an obstruction. Microwaves do not diffract and therefore the transmitter and receiver needs to be in line of sight. |
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