COMPUTER STUDIES QUESTIONS WITH ANSWERS
Highlight three categories of radio waves.
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Define the term 'unguided transmission media'.Unguided transmission media transmit signals from the source to the destination but do not force the signals to pass through restricted paths. Electromagnetic waves are examples of unguided transmission media. State three examples of unguided transmission media.
Study Table below and match the characteristics in the first column to the cable type by marking with an x in the appropriate column.State five advantages of using fibre optic as a transmission media.
Differentiate between single mode and multimode fibre optic cables.A single mode fibre optic cable has a very thin core hence, it can only receive a single ray of light while a multimode fibre optic cable has a thick core and can receive multiple light rays. Light in the multimode cable attenuates faster than in the single mode. State one application area for each mode of fibre optic cables.
Using an illustration, explain how a fibre optic cable transmits data.Light pulses carrying data are projected into the cable at the source in such a manner that the angle of incidence is greater than the critical angle of the core. The light in the core tries to penetrate the cladding. Since the cladding is of higher refractive index, total internal reflection occurs. The light is kept within the core, bouncing off the boundary of the core and cladding until it reaches to the destination.
Using a diagram, explain the physical structure of a fibre optic cable.The core of a fibre optic cable is made up of transparent glass or plastic. Surrounding the core is a more dense material of higher refractive index than the core called the cladding. The outer protective layer or jacket protects the cable from mechanical harm.
With the aid of a diagram, describe the physical structure of a coaxial cable.Coaxial cables are made up of a central copper core that is insulated with a dialectric material (insulator), an aluminium foil, a braided shield (or mesh conductor) and an outer plastic covering. This insulation makes the cable resistant to electromagnetic interference.
Describe the electrical properties of coaxial cables that made it suitable as a network backbone before the advent of fibre optic cables.Coaxial cables support high bandwidth compared to UTP cables; hence, a preferred choice for laying network backbones. In addition, it conducts data using direct current and is more immune to electromagnetic interference thus it is preferred for EMI prone places.
Using illustrations, differentiate between thinnet and thicknet coaxial cables.A thinnet or thin coaxial cable has one dielectric insulator (Fig. 1.5 (a)) while a thicknet or thick coaxial cable has two dielectric insulators (Fig. 1.5 (b)).
List five sources of electromagnetic interference that may cause data loss in communication systems.19/11/2022 List five sources of electromagnetic interference that may cause data loss in communication systems.
ADVANTAGES OF SETTING UP A COMPUTER NETWORK USING TWISTED PAIR CABLES
Disadvantages OF SETTING UP A COMPUTER NETWORK USING TWISTED PAIR CABLES
State the components needed for each of the following task in a fibre network.
Using illustrations, differentiate between unshielded and shielded twisted pair cables.The two types of twisted pair cables are made up of two insulated copper wires wound around each other to form a helix.
However, the unshielded twisted pair (UTP) cables do not have an external shield to guard against electromagnetic interference (EMI) from the environment as shown in Fig 1.3 (a). Shielded twisted pair (STP) cables, on the other hand, have an external shield which guards against environmental EMI (Fig. 1.3 (b)) Why is the use of the two wire open lines cables not common nowadays.The cables suffer from electromagnetic interference (EMI) because they are not shielded from environmental 'noise'. They pick electromagnetic signals from the environment; hence, they introduce noise in the communication channel. The magnetic fields around individual cables also interfere with each other during transmission leading to high radiation losses through a process called crosstalk.
Describe how the two wire open lines cable works in data transmission.The cable is made up of two copper wires running parallel to each other and separated by a plastic insulator. The copper wires are good signal conductors and are cheap to buy.
Communication media can be classified into two broad categories. State the two categories giving examples of each.
List four types of guided transmission media.
List four examples of wide area networks (WANs).
Apart from size, what other properties are unique to LANS as opposed to MANS or WANs?
The following are acronyms for some types of networks. Write them in full.
Computer networks can be classified according to their geographical size and ownership. Explain each of the following with regard to this classification. (a) LAN (b) MAN (c) WAN
State five limitations of networking.
State five reasons why computer networks are important.
Identify two application areas each where simplex, half- duplex and full-duplex communication modes are used. Simplex communication is used in public broadcasting where receivers do not have to reply, for example, in radio and television broadcasting; some missile launching systems which only receive commands from the launcher, and are not set to communicate back. Half-duplex communication is used in two way (one way at a time) high frequency radios such as the walkie-talkie radios;half-duplex ethernet where only one computer is allowed to use the transmission media at a time. Full-duplex communication is used in computer networks such as in full-duplex ethernet networks where one pair of UTP cable is used for sending data and another one for receiving; voice telephone networks (mobile phones) where one frequency is set for sending and another one for receiving data (also called frequency-division duplex).
When you look at water bodies like lakes or seas, the water appears blue from a distance yet at a closer look it is colourless. Explain this phenomena. The seven colours in white light have different attenuation distances in water, with blue having the longest attenuation distance. Therefore, when the light strikes vast water bodies, the other colours attenuate faster (are filtered) leaving the predominant blue colour. Hence, the deeper the water body, the more blue it appears.
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