Question 1: Define electromagnetic spectrum and name three types of waves used in communication.

Answer: Electromagnetic spectrum is the range of all types of electromagnetic radiation. Three types used in communication are radio waves, microwaves, and infrared waves.

Question 2: Explain how radio waves are used to transmit television signals.

Answer: Radio waves carry television signals by modulating the signal onto a carrier wave, which is transmitted via aerials. The TV receiver demodulates the wave to extract the picture and sound information.

Question 3: What is the main advantage of using microwaves for satellite communication?

Answer: Microwaves can pass through the Earth's atmosphere with minimal attenuation and can be used for long-distance communication with satellites.

Question 1: Calculate the wavelength of a microwave used in satellite communication with a frequency of 12 GHz. (Use the speed of light, c = 3 x 10^8 m/s).

Answer: Wavelength (λ) = c / f = (3 x 10^8 m/s) / (12 x 10^9 Hz) = 0.025 m.

Question 2: A fibre optic cable transmits infrared signals at a wavelength of 1.55 μm. What is this wavelength in metres?

Answer: 1.55 μm = 1.55 x 10^-6 m.

Question 1: Describe a simple experiment to demonstrate how radio waves can be transmitted and received. Include the key variables and safety precautions.

Answer: Students can set up a basic radio transmitter and receiver circuit, ensuring the transmitter is operated at a safe power level. The experiment involves transmitting signals over a short distance, varying the transmitter power and antenna orientation to observe effects on reception quality. Variables include frequency, power, and antenna position. Safety precautions include avoiding high power levels, ensuring proper insulation, and operating within legal frequency bands.

Question 1: A mobile phone uses radio waves with a frequency of 900 MHz to communicate with a cell tower. If the signal is received with a delay of 3 milliseconds, estimate the maximum distance between the phone and the tower.

Answer: Distance = speed x time = (3 x 10^8 m/s) x 3 x 10^-3 s = 900,000 m or 900 km.

Question 1: Explain the advantages and disadvantages of using microwaves for wireless communication. Include safety considerations in your answer. (6 marks)

Answer: Microwaves allow high data transmission rates and can cover large distances with minimal loss, making them ideal for satellite and mobile communication. However, they require line-of-sight and are susceptible to weather interference, such as rain. Safety considerations include avoiding exposure to high microwave levels, which can cause heating of tissues, and ensuring equipment complies with safety standards.

Question 1: Describe how infrared waves are used in remote controls and the considerations for their safe use.

Answer: Infrared waves are used in remote controls to transmit signals wirelessly to devices like TVs. They are safe because infrared radiation is non-ionising and has low energy, but direct exposure at close range should be limited to prevent potential heating effects.