(a) Differentiate between the renewable and non-renewable sources of energy giving example of each one of them. (b) Give a brief account of optic fibers. What is their importance in present day telecom system? (c) What is the most dangerous part of hurricane and how do cyclone affect humans? (d) What is the difference between vaccines and Antibiotics? How do antibiotics and vaccines contribute to health?

(a) Renewable and non-renewable energy

Replenishment: renewable sources are naturally replaced on a human timescale, while non-renewable sources exist in limited stocks and take millions of years to form. Pollution: renewable sources generally produce few emissions during use, whereas burning fossil fuels emits CO₂ and other pollutants. Availability: solar and wind vary with weather and season, whereas fossil fuels can be stored and used on demand. Examples of renewable sources: solar, wind, hydropower, geothermal and biomass. Examples of non-renewable sources: coal, oil, natural gas and nuclear fuels such as uranium.

(b) Optic fibers

An optic fiber is a hair-thin strand of very pure glass or plastic that carries information as pulses of light. It has a central core with a higher refractive index, surrounded by cladding with a lower refractive index and a protective coating. Light travels along the core through repeated total internal reflection.

Importance in telecommunication

(i) very high bandwidth, so it can carry huge amounts of voice, video and internet data; (ii) low signal loss, allowing long distances with fewer repeaters; (iii) immunity to electromagnetic interference, as it carries light, not electric current; (iv) greater security, as it is hard to tap unnoticed; (v) light weight and small size compared with copper cables.

Optical fibres form the backbone of modern networks, including undersea cables, mobile network links, and fibre-to-the-home connections.

(c) Hurricanes and cyclones

Most dangerous part: the eyewall, the ring of towering storms around the calm central eye, has the strongest winds and heaviest rain. In terms of the loss of life, however, the greatest danger usually comes from the storm surge, in which wind pushes seawater onto low-lying coasts.

Effects on humans

Loss of life: drowning from surge and flooding, and injuries from flying debris. Destruction: damage to homes, roads, bridges, and power and communication lines. Livelihoods: loss of crops, livestock, boats and businesses, and saltwater damage to farmland. Health: contaminated water and outbreaks of waterborne disease, along with psychological trauma. Displacement: people may be forced to leave their homes for long periods.

The 1970 Bhola cyclone in what was then East Pakistan killed an estimated 300,000 or more people, showing how severe the surge in a low-lying delta can be. Early warnings and evacuation have since greatly reduced deaths in the region.

(d) Vaccines and antibiotics

Purpose: vaccines prevent disease, while antibiotics treat bacterial infections. Action: vaccines train the immune system to recognise a pathogen. Antibiotics kill bacteria or stop their growth. Target: vaccines exist for both viral and bacterial diseases. Antibiotics act only against bacteria and do not work on viruses. Timing: vaccines are generally given before exposure. Antibiotics are given once there is a bacterial infection. Duration: vaccine protection can last years, while antibiotics act only during treatment. Resistance: bacteria increasingly become resistant to antibiotics, whereas resistance to vaccines is less common.

Contribution to health: vaccines have eradicated smallpox, nearly ended polio, and reduced measles, tetanus and diphtheria; they also protect those who cannot be vaccinated, through herd immunity. Antibiotics have made pneumonia, tuberculosis and wound infections far more treatable, and they make surgery, cancer therapy and childbirth much safer. Together, they have greatly reduced deaths from infection.