3.3 Electromagnetic spectrum (3)
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1.
Describe typical uses of the different regions of the electromagnetic spectrum, including:
- Radio waves: radio and television transmissions, astronomy, radio frequency identification (RFID)
- Microwaves: satellite television, mobile phones (cell phones), microwave ovens
- Infrared: electric grills, short range communications such as remote controls for televisions, intruder alarms, thermal imaging, optical fibres
- Visible light: vision, photography, illumination
- Ultraviolet: security marking, detecting fake bank notes, sterilising water
- X-rays: medical scanning, security scanners
- Gamma rays: sterilising food and medical equipment, detection of cancer and its treatment
The electromagnetic spectrum is a range of electromagnetic radiation, classified by frequency and wavelength. Different regions of the spectrum have distinct properties and are utilized for various applications. Here's a description of typical uses for each region:
Radio Waves: Radio waves have long wavelengths and low frequencies. They are commonly used for radio and television transmissions, where signals are broadcast over long distances. In astronomy, radio waves are used to study celestial objects that emit radio signals. Radio Frequency Identification (RFID) uses radio waves to identify and track objects, often used in inventory management and access control.
2.
The electromagnetic spectrum is often described as a continuous range of waves. Explain why this is a useful way to describe the spectrum. Include a description of the relationship between frequency and wavelength.
Describing the electromagnetic spectrum as a continuous range of waves is useful because it highlights the fact that the different regions are not sharply defined with clear boundaries. Instead, there's a gradual transition between them. The frequency and wavelength of electromagnetic waves are inversely proportional. This means that as the frequency of a wave increases, its wavelength decreases, and vice versa. The relationship is given by the equation: v = fλ, where v is the speed of light (approximately 3 x 108 m/s), f is the frequency, and λ is the wavelength.
3.
Optical fibres, using visible light or infrared radiation, are commonly used in cable television and high-speed broadband networks. Explain why optical fibres are an effective medium for transmitting data, and describe the properties of light that make this possible.
Optical fibres are an effective medium for transmitting data because they use total internal reflection to guide light signals over long distances.
The key property of light that makes this possible is its ability to undergo total internal reflection. When light travels from a denser medium (the core of the fibre) to a less dense medium (the cladding), it can be reflected back into the denser medium if the angle of incidence exceeds the critical angle. This repeated reflection keeps the light confined within the fibre, allowing it to travel long distances with minimal signal loss.
Furthermore, the use of transparent glass (or plastic) for the fibre core ensures that light is not significantly absorbed as it travels through the fibre. This allows for high-speed data transmission with minimal signal degradation, making optical fibres ideal for cable television and high-speed broadband applications.