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Group 5 Main Page

Page history last edited by the assassin 11 years, 5 months ago

Group 5 Main Page(Part 1)

 

This is Part 1 of 2.

 

Group 5:

5 Aspects to remember

 

1.  One ultimate target

2.  To salute to scientists and environmentalists

3.  3 is less (better) than 4.

4.  For the sake of maximising usage of what is available

5.  5 letters in the word "group".

 

G - Go for the goal

R - Restless everyday

O - Opposing twisted facts and misconceptions with evidences

U - Unsure of anything? Google it.

P - Promising future in terms of everything, we shall believe

 

5 - 5 Aspects above: Remember it.

 

Members and Roles

 

Index Number Name  Role(s) in the Group 
5 Trevor Ching Hao Ye 

Overall in charge of procedures;Leader

The Supervisor,El lider, El Amante

18  Lee Hern Yi 

El Tirador ; Accurate and sharp

The Compatriot + The Crafter + The Blacksmith ( Artefact)

In charge of other PBL stuff/ Crafting,design and making

Fond of a 2I1 girl(leave to other's decision to reveal or not)

20  Lim Fang Yi 

Fully in charge of Main Pages of PBL and IPW and how light travels

Page Editor + Researcher

El ocupados una 

33  Ting Rong Xiang 

(The fellow Malaysian + Singapore PR) + The Questioner

The Cool One + The Entertainer/Joker + The in charge of some PBL stuff + The Playboy + El Animador + The designer of artefact (box)

 

Crisis and Problem faced by the World

 

A United Nations meeting

 

1. Global Warming 

2. Climate Change 

 

Global warming is too serious for the world any longer to ignore its danger or split into opposing factions on it. - Tony Blair

 

All across the world, in every kind of environment and region known to man, increasingly dangerous weather patterns and devastating storms are abruptly putting an end to the long-running debate over whether or not climate change is real. Not only is it real, it's here, and its effects are giving rise to a frighteningly new global phenomenon: the man-made natural disaster. - Barrack Obama

 

Non-renewable sources Of Energy

 

1.Fossil Fuels

Coal

Crude oil

Natural gas power plant

Fossil fuels, as you know, is our most commonly used source of energy. Examples include coal,oil as well as natural gas. Oil is formed,when the remains

of plankton are compressed under heat and pressure and under the seabed for many years. Oil is a useful fuel as it provides a large amount of energy and can be easily transported over long distances via pipelines and tankers. However, use of fossil fuels causes air pollution.Also, fossil fuels are exhaustible and fast depleting. Oil is expected to run out in about 30-70 years, natural gas in 50 to 120 years and coal in about 300 years.

 

2.Nuclear Energy

Nuclear power plants

]

Nuclear reactor diagram

Nuclear Fission

Nuclear Fusion

 

Nuclear energy is the energy possessed in an atom. It is released during nuclear fission or fusion, the processes of splitting or combining of atoms respectively.Nuclear fission and fusion takes place in the nuclear reactors.(An additional information here: Nuclear fusion takes place in the core of the Sun. The Sun's main components are Hydrogen and Helium, and the Sun actually uses six hundred million tonnes of Hydrogen to conduct nuclear fusion per second.As a result the Sun gives out a large amount of heat and light due to nuclear fusion)Nuclear fission and fusion release an enormous and tremendous amount of heat and light. The heat released is then used to heat the water into steam, which the steam in turn is used to drive the turbines,which is connected to the generator to generate electricity. The water in the cooling system cools the steam and the steam condenses into water then it is pumped back to steam generator.then the cycle continues again. A nuclear fuel is Uranium which is radioactive and non-renewable. However, the nuclear energy has its disadvantages as well. Two very famous cases of nuclear incidents were the Chernobyl disaster in former Soviet Union(now Ukraine) and the recent Fukushima I nuclear disaster. The enormous amount of energy produced at the reactors requires strict and careful controls. Not only so, nuclear waste has to be carefully contained and disposed of. In addition, nuclear power plants have life spans of about only 30 years and cannot be dismantled due to possibility of radioactive contamination.(where the radioactive substances radiate in a certain area and makes it not possible to have humans settlements in this affected area)

 

Solutions(Renewable sources of energy)

 

 

1. Exploit and use renewable sources of energy instead

 


2. Reduce usage of fossil fuels

BMW Hydrogen 7, which runs on liquid hydrogen.

 

Honda FCX Clarity,a hydrogen fuel cell vehicle, but it is a car with zero emissions,only leaving water vapour(still a greenhouse gas) behind.

 

Definitions

 

 

1. What is energy?

 

 

Energy is defined to be the ability to do work. 

 

2. What are renewable sources of energy?

 

 

They are sources of energy that are limited in supply and will eventually run out one day,

 

3. What is global warming?

 

 

Global warming refers to the situation when when the earth heats up and its temperature increases.  It happens when too much greenhouse gases like carbon dioxide, water vapour, nitrous oxide, and methane trap the heat and light coming from the sun in the earth’s atmosphere, and prevents heat from escaping to outer space.  This is known as greenhouse effect, except it is in a more serious way. 

 

Renewable sources of energy

 

1. Hydroelectric (Focus)

 

2. Geothermal

 

The Earth's core is so hot that metals melt there, Heat contained within the Earth's core is called geothermal energy. Volcanoes, hot springs as well as geysers provide outlets for which the heat can escape. Geothermal power plants are built near these areas where water is pumped underground to be heated and turn into steam,then the steam is used to turn turbines to drive the generators and producing electricity. It is renewable and free. However, you cannot build geothermal power stations anywhere you like. They can only be built in certain areas as geothermal emissions contain environmental pollutants like boron and sulphur oxide.

 

3. Wind 

 

Wind is moving air.It is caused by the differential heating of Earth by the Sun, resulting in varying pressures of air at different regions.  Wind is produced when air from areas of higher pressure flows towards areas of lower pressure. Traditional windmills convert kinetic energy of wind into mechanical energy to pump water or grind food,while modern wind turbines use this kinetic energy to drive generators,and generate electricity. This renewable source of energy is free and do not cause pollution.

 

4. Tidal

 

Tides are caused by gravitational pulls of Moon(If you didn't know why the Moon would not fall to the Earth,the Moon also rotates and revolves around Earth and gain centrifugal force to overcome the gravity of Earth), and Sun(but to a lesser extent) on waters and oceans. Tidal energy refers to the energy that water from seas or oceans has due to the difference in its height at high and low tides. Tidal energy is then used to turn turbines at tidal power stations and generating electricity. Tidal power plants are built across the mouth of a tidal river or an estuary,harnessing kinetic energy of the flowing water.

 

5. Solar

Mono-crystalline Solar panel(photovoltaic cells)

 

Solar Energy is our main source of energy and it comes from the Sun.It provides energy in the forms of heat and light.This energy is then used directly or indirectly by living things to do work,for example, photosynthesis. The Sun's energy can be stored in photovoltaic cells and solar panels and directly converted into electricity. Solar energy is free, readily available and does not pollute the environment. However, solar tapping devices are expensive and are bulky, requiring a lot of space.

6. Biomass

Some organic waste(like methane) from industries such as agriculture and construction can be converted into liquid or gaseous fuels. This, together with other forms of organic waste,can be burnt in biomass power plants, generating electricity. The energy produced is known as biomass energy Biomass energy is renewable and do not cause much air pollution, but the amount of energy produced is usually very little.

 

7. Hydrogen 


 

A hydrogen power plant is a concept design for a new widespread electricity source. It is a facility which uses hydrogen to produce electricity. First of all, liquid hydrogen is fed into hydrogen fuel cells. The fuel cells contain an electrolyte fluid and two terminals. The hydrogen and oxygen(reactants) flow into the cells. They intermingle with the electrolyte to produce electrical charges, and water(as a byproduct). The water flows out another port while the electricity is siphoned off the terminals and stored in multi-ton, gigantic batteries. When the electricity is needed, it is sent out through the local power grid just like any other types of power plants. Theoretically, it is a nearly perfect source of energy as it has no dangerous byproducts and has a high efficiency in fuels as the average internal combustion engine. However the disadvantage is that it is not easy to obtain hydrogen, and it is very expensive. 

Main focus: Hydroelectricity

 

Three Gorges Dam,长江三峡大坝,its hydroelectric plant has the largest capacity of generating electricity in the world It was built across the Yangtze river, serving purposes of generating hydroelectricity, control floods by draining excess water to a storage area and increase the river's shipping capacity.

 

What is hydroelectricity?How does it work?

 

It refers to generating electricity using gravitational potential energy of falling or flowing water. Water at high altitude areas possess large amount of gravitational potential energy.When flood gates of dam open, the flowing water is converted into kinetic energy then the turbine spin the generator to generate electricity at hydroelectricity plants.

 

The advantages of hydroelectricity?

1. Cost wise -

 

 

No fossil fuels needed, and operation cost of a hydroelectric plant is almost not affected by increased price of fossil fuels. Because the plant is operated almost automatically, cost of labour is not high as not much labour needs to be employed. Moreover, multi-purpose dams can be built along with a hydroelectric plant which is not very expensive to built, and the sale of generated electricity can cover the cost of construction of dam in merely few years time.

 

2. Emissions-wise -

 


 

Because fossil fuels need not be burnt, there will not be direct emissions of greenhouse gas carbon dioxide. Still however, researches have shown that hydroelectric plants produces least emissions compared to other energy sources.

 

3. The "dam" factor -

 

 

Because a dam is built alongside an hydroelectric plant, the hydroelectric plant's other advantage would be due to the water dam. The water dam would form an artificial reservoir behind it. When heavy downpours lead to increase in water level, the dam would be able to drain the water by opening up the flood gates to minimise opportunities of floods from occurring.

 

The disadvantages of hydroelectricity?

 

The Glen Canyon dam located at the Grand Canyon in North America. It serves the purpose of generation of electricity, storing water for water-scarce South-Western America and providing the water used for recreational activities.

 

1. Increased land constraints and indirect and directly damages the ecosystem - 

 


 

Large reservoirs needed to operate hydroelectric plants result in submerge of extensive areas upstream of the dams, lowland and riverine valley forests, marshland and grasslands. The loss of land is often worsened by the fact that reservoirs cause habitat fragmentation(when discontinuities emerge in a species of organism's habitat) of surrounding areas.

Hydroelectric projects can harm surrounding aquatic ecosystems, upstream as well as the downstream of the location of the plant.Dams reduced the population of salmons by preventing them to move to spawning grounds upstream, even though dams located at salmon habitat have fish ladders. Salmon spawn are also affected on their migration to sea when they must swim through turbines. As a result some areas transporting smolt downstream by barge. Dams,were demolished due to the drastic decrease in fish population.Producing hydroelectric power modifies the environment of river downstream. Water that moves out from turbines most of the time contains very little suspended sediment, which can cause river bed scours and riverbank losses. Since turbine gates are often opened intermittently, examinations rapid or even daily fluctuations in river flow are present. In the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon Dam was found to causing erosion of sand bars. Dissolved oxygen content of the water may change after construction of dam. Depending on the location, water exiting from turbines is typically much warmer than the previous water, which can change aquatic faunal populations, including endangered species, and prevent natural freezing processes from occurring. Sometimes, canals divert a river at a shallower gradient to increase the head of the scheme. The entire river may be diverted causing a dry river bed.

 

2. Siltation  -  

 

 

Siltation can fill a reservoir and decreases its capacity to control floods as well as causing additional horizontal pressure on the upstream parts of the dam. As a result, some reservoirs can become completely full of sediment and useless or over-top during a flood and fail.

 

3. Flow amount changes -  

 

 

Changes in amount of river flows, will affect the amount of hydroelectricity produced. Lesser amount of river flows that may be caused by droughts, climate change , or upstream diversions and dams which are located more of upstream river. As a result lesser river flow will result in lesser turning of turbines and generators.

 

4. Methane released by reservoirs -

 


 

Lower positive impacts are found in the tropical areas, as it has been noted that the reservoirs of power plants in tropical regions may produce methane gas considerable amounts ,due to plant material in flooded areas decaying in an anaerobic environment, and forming methane, which is a very powerful greenhouse gas. According to reports, where the reservoir is large compared to the generating capacity (less than 100W/m2 of surface area) and no deforestation in the area was undertaken prior to impoundment of the reservoir, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant. Although these emissions meant that presence of carbon in the biosphere, not fossil deposits that had been sequestered from the carbon cycle, there is a greater amount of methane due to anaerobic decay, causing greater damage than would otherwise have occurred had the forest decayed naturally.

A new level of underwater logging operation that aims for drowned forests can help in less worsening of the effect of decay of forests.

 

5. Relocation of people mainly due to land constraints

 


 

Another disadvantage of hydroelectric dams is the need to relocate the people living at sites of planned dam construction. It was once estimated that around 40 to 80 million people worldwide had been physically displaced  due to construction of dams. In many cases, no amount of compensation and amendments can overtake or substitute the ancestral and cultural attachments to places that have spiritual and important value to these displaced population. In addition, historical and culture sites can be flooded and lost.

Examples of such cases surfacing of of water include the Aswan Dam in Egypt between 1960 and 1980, the Three Gorges Dam in China, the Clyde Dam in New Zealand, and the ilusu Dam in Turkey.

 

How hydroelectricity is being used in other countries

 

 

China : Three Gorges Dam      

 

 

Note: MW stands for megawatts

 

It powers itself with self-generated electricity. It has 26 turbines, 700 MW each, a total of 18 200 MW, but six more turbines will go into operation in 2012. Totaling up the 32 turbines and the 2 smaller generators of 50 MW, the total hydroelectricity generated reach 22,500 MW when the other six turbines go into operation. The to total hydroelectricity generated will more than 100 Tera-Watt hours (TWh) when all 32 turbines are put in operation.  The dam was expected to provide up to 10% of total electricity usage. Nine of the provinces and two of the cities in China, share the generated hydroelectricity from the dam's hydroelectricity plant.

 

Other uses: It created an artificial reservoir behind the dam, and is used for security. It was reported that People's Liberation Army General mentioned about the dam could be used as a military defensive wall to protect themselves from invasion.

 

United States Of America: Hoover Dam

 


 

Hoover dam, is a concrete arch-gravity dam, which means that it is built with concrete and curved to curve upstream of river water so that hydrostatic pressure(force of water against the dam) presses against the arch so that the structure of dam can be strengthened and compressed as the hydrostatic pressure pushes into the dam's foundations. On the other hand, arch-gravity dams' stability is secured by making the dam's shape and size to resist overturning,sliding and crushing at the toe. Hoover Dam is built in the Black Canyon of the Colorado River. The water from Lake Meads enters the intake towers, then 4 penstocks which funnel the water downwards, then passes through the turbines. Now, the total gross power rating for the hydroelectricity plant,including the two 2.4MW that self-powers the Hoover dam's operation, hits a total of 2080 MW. However, the generation of hydroelectricity by Hoover Dam varies. When the highest in 1984, it generated a maximum of 10.348 TWh, and the minimum generation of 2.648 TWh in 1956 since 1940. Up to present, the average generation of hydroelectricity hits about around 4.2 TWh per year.

 

Possibility Of Usage of Hydroelectricity in Singapore

 

Marina Barrage

 

Singapore, although it has Marina Barrage, a dam, but hydroelectricity plants have not been adopted due to Singapore's lack of water(because now water catchment areas even occupy two-third of Singapore's land area) hence it is not possible to have hydroelectricity until we can find more and effective sources of water supply. Building of Marina Barrage created the 15th reservoir of Singapore artificially. Marina Barrage's have three main purposes: Water Supply, Flood Control, and Recreational activities. Moreover Singapore would not have more land to build another dam for hydroelectricity should due land scarcity and constraints. 

 

Reducing usage of fossil fuels...

 

 

(i) Electrical energy used for lighting in the homes/buildings

 

(ii) Electrical energy used for cooling of the homes/building

 

Shading Devices(Lighting + Cooling)

 


 

 

Shading devices and provide cooling and lighting of buildings.The usage of Solar control and shading devices is a vital aspect of energy-efficient buildings. In particular, buildings using passive solar heating or daylighting relies on sun control and shading devices.During hotter seasons, external window shading is a way to prevent unwanted heat from sun to entering a space. Shading iis provided by natural landscaping or by building elements. Shading devices can also be used as reflectors, called light shelves, which bounce sunlight for lighting into building interiors.The design of shading devices relies on the solar orientation of a particular building facade. For instance, simple fixed overhangs are very effective at shading south-facing windows in the summer when sun angles are high. However, the same horizontal device is  not effective at blocking low afternoon sun from entering west-facing windows during maximum heat gain periods during summer.Exterior shading devices are very effective when used together with clear glass facades. However,high-performance glazings are now available that have very low shading coefficients (SC). When specified, these new glass products reduce the need for exterior shading devices.Solar control and shading can be provided by a wide range of building components including: 1. Landscape features like mature trees;  2. Exterior elements such as overhangs or vertical fins;  3. Horizontal Reflecting surfaces known as light shelves; Usage of low shading coefficient glass;  4. Interior glare control devices like Venetian blinds or adjustable louvers.Fixed exterior shading devices such as overhangs usually more effective for small commercial buildings. The optimal length of an overhang depends on the size of the window and the need for heating and cooling in the building.To design shading devices it is needed to understand the position of the sun in the sky during the cooling season. The position of the sun is expressed in terms of altitude( angle of the sun above the horizon, achieving its maximum on a given day at solar noon) and azimuth angles(angle of the sun's projection onto the ground plane relative to south).

 

 

Mirror ducts: (Lighting)

Features of a mirror duct in a room.

 

Natural light can be introduced into buildings by two ways using mirror ducts. The first one is horizontal, where light is captured at walls. The other one is vertical where light is admitted from rooftops. The mirror duct system does not need energy for operating it or for maintenance, hence it requires less electricity consumption. Another advantage is the reduced Carbon Dioxide emission from the lighting power consumption will be cut down drastically. Moreover there are filters that filter out the Ultraviolet rays to provide safe and healthy lighting in the room.

 

Light pipes (Lighting)

 


 

Light pipes placed on roofs of building collect sunrays and are reflected using mirrors placed at the ducts, will throw the daylight into the room, then spread around throughout the rooms by diffusers.

 

Automatic light level adjustment(Lighting):

 


 

A complex circuit with many sensors within a room. When the sensor detects sufficient light in the room, artificial light powered by electricity will totally turn off automatically. When there is not enough light, the amount of artificial light varies according to how much level of light is away from the sufficient standard.

 

Floor vents(Cooling):

 

 

Under floor ventilation systems use the space beneath raised floors as a plenum, to separate air using diffusers into the occupied space. usually passive or active swirls are used for diffusers . UFAD systems are characterized by their ability to allow each individual occupant  to have a degree of control of the environment around them. UFAD systems benefit from a floor to ceiling airflow pattern that makes use of the natural buoyancy from heat sources in the occupied space. It is comparable to displacement ventilation systems(where cooling is supplied from floor level at low velocity. This cool air mix with warm air in the space and rises towards the ceiling where it is extracted) where a temperature stratification occurs in the ventilated room. This can be used as a beneficial way to reduce the cooling load as the cooling load removed from the room is proportional to the difference in temperature between the supply air and extracted air. As a result, it brings in energy savings when the cooling coil in the air conditioning unit is operating. Furthermore, free cooling can be used for longer periods of the year. 

 

Greenery(Cooling)

 

 

The plants planted on walls will shade walls from direct exposure from sunlight and heat and lower temperature, or planted at rooftops to reduce temperature of the highest level of the building. This is because the plants act as a cover, by absorbing the heat for warmth and light for photosynthesis. Transpiration of the plants is another reason. When the plants transpire, some of the water vapour may condense on the building. So if the water evaporates, they will take away some heat from the building.So the two effects take place simultaneously and keep the building cool.

 

Colour of paint(Cooling)

This we know; If an object's colour is one of the primary colours, it has that primary colour because it absorb all other primary colours of light except for its own colour. So, if the building is painted with darker colours, the darker colours absorb more heat than lighter colours and hence more energy have to used for cooling the building and rooms so amount of energy consumption is higher. Similarly, if the building is painted with lighter colours, the lighter colours absorb less heat than darker colours so less energy will be needed for cooling the building or rooms hence amount of energy consumption will be lower.

 

Solar Chimneys(Cooling)

 

 

Solar Chimney, is a method of improving natural ventilation of buildings by taking the advantage of convection(Transfer of heat from one place to another by the movement of fluids. A fluid of a given density rises within another fluid of a higher density and sinks within a fluid of a smaller density).Glass collector draws the ambient air. This is warmed by solar energy and moves up the chimney. The current of rising warm air spins a turbine. Although the capital cost is high,running costs are very low.To add on,the fuel is free and the power station has a long lifetime. The overall conversion efficiency from solar energy to electricity is 2-3%., and the remaining are gone due to these factors: 1. Decrease in temperature with altitude of about 10° C for a 1000 metre chimney2. Large quantities of warm air have to be lifted from the ground to chimney top. Energy is lost here. 2. The air that leaves the chimney is above ambient temperature at that altitude. This is thermal energy lost. 3. Ambient air that is drawn into the collector and is warmed expands with slight rise in pressure. Most of solar input is lost in the simple expansion of air before it reaches the turbine. None of this is lost to the turbine. Hence, sometimes regenerators are added.

 

Personalised Ventilation(Cooling)

Sit down at your desk and you will receive your very own, personalised fresh,cool air.The personalised ventilation system delivers fresh air directly to each occupant through attached pipes to their desks.

 

Single Coil twin Fan Ventilation system(Cooling)

 

The fan will separately cool fresh air and recirculated air, which leads to efficient usage of energy. Presence of occupants is detected by sensors and the cooling required is supplied accordingly.

 

Going Further: Solutions to transportation with 0/minimum emissions? 

Hydrogen fuel-celled cars and Hydrogen Internal Combustion engine vehicles

 

BMW Hydrogen 7 refilling liquid hydrogen at a designated liquid hydrogen station.

 

hydrogen vehicle is an alternative fuel vehicle that runs on hydrogen as its onboard fuel for motive power.The advantage of using hydrogen as an energy currency is that, if hydrogen is prepared without using fossil fuel inputs, vehicle propulsion would not contribute to carbon dioxide emissions and leaving only water vapour or in its liquid form instead. The disadvantages of using hydrogen as fuels are low energy content per unit volume, high tankage weights, very high storage vessel pressures, the storage, transportation and filling of gaseous or liquid hydrogen in vehicles, the large investment in infrastructure that would be required to fuel vehicles, and the inefficiency of production processes.

 

 

Solar-powered cars

 

 

solar vehicle is an electric vehicle powered by solar electricity. This is obtained from solar panels on the surface (generally, the top or window as shown in the picture) of the vehicle.  the photovoltaic cells on the solar panels convert the sun's energy directly into electrical energy.

 

1.  Cost wise-While sunlight can provide a free,clean source of energy, the creation of photovoltaic cells to capture that sunlight and convert it is expensive. Years ago, it was found that energy would cost $0.30/kWh which is much more expensive that of residential electricity.These costs have dropped recently with Solar Panel costs coming down further and the reliability of the cells have much improved with thinfilm technology. The cost of energy depends on the place of operation as solar radiation differs from place to place.

2.  Lifetime wise - Even though sunlight has a long lifespan(5 billion years), photovoltaic cells do not. The lifetime of a solar module is around 30 years. Standard photovoltaics often come with a warranty of 90 % (from nominal power) after 10 years and 80 % after 25 years. However, in automotive purposes they need to be sealed well under certain circumstances if meant to operate efficiently for many years in different weather conditions. The photovoltaic cells can further be damaged due to pollutions.

 

Battery Electric Vehicle(BEV)


Tesla Roadster

 

 

battery electric vehicle, or BEV, is a type of electric vehicle (EV) that uses chemical potential energy stored in rechargeable dry cells packs(Electric Vehicle Battery or Traction battery) to run.Like other electrical vehicles, BEVs make use of electric motors and motor controllers and not internal combustion engines for propulsion.The motor controller regulates the power to the motor, supplying either variable pulse width DC or variable frequency variable amplitude AC, depending on the motor type, DC or AC.

 

Electric Car

 

 

Tesla Model S

 

An electric car is a plug-in(charged) battery powered automobile which is propelled and powered by electric motors. They are more expensive than cars that run on petrol due to high cost of battery replacements. The running and maintenance costs compared to gasoline cars is a factor as well, because these cars incur less maintenance fees if their batteries are Lithium-ion batteries. 

 

 

How Light Travels

 

There is unlimited source of sunlight in the opening but how can it be directed into the rooms? By using mirrors, the light rays can be directed into a room. So how does the mirror redirect the direction of the light rays? Can the light rays be spread out over a larger area? What else can we used to replace mirrors at every turns and bends? 

 

 Useful websites

http://zonalandeducation.com/mstm/physics/light/rayOptics/refraction/refraction1.html

http://www.physicstutorials.org/index.php/home/optics/refraction-of-light/the-laws-of-refraction (no need to read about snell's law)

http://omlc.ogi.edu/classroom/scat_demo/

http://www.solatube.co.uk/trade/solar-light-tube-for-professional-builder/how-solatube-works/index.php

http://www.just-rooflights.com/

  

 

1. How Light Travels?

 


 

Light travels in a straight line at a speed of 299,792,458 m/s in a vacuum, which is very much faster than sound(340.29 m/s)

 

 

2. How is the light rays reflected off the surface of a plane mirror?

 

 

When the light rays hit the surface of a plane mirror, a regular reflection takes place and the parallel beam of light remain parallel before and after the reflection. Law of reflection of light is still observed( the normal, incident ray and reflected ray all lie to the same plane and the angle of incidence = angle of reflection)

 

 

3. Can light rays bend? What is it if so?How does it occur?How does light bend when it travels from a medium to another?

 

Refraction Diagram

 

Light rays can bend.Light ray bends when a light ray travels from one medium to another medium of a different density, the light ray changes direction and will bend.This bending of light is known as refraction. At the point where the ray enters, a normal is drawn. When light enters a medium of a higher density, the ray of light will bend towards the normal. When light exits the medium, to another medium of lesser density, the ray of light will bend away from the normal.

 

 

4. Give an example of refraction.

 


 

When you put a steel spoon into a glass of water, the spoon looks distorted because the light reflected by the spoon enters the water(which has greater density) and bends toward the normal. When the light exits the water, the light will bend away from the normal and then enter into our eyes.

 

5. Diffusion of light rays

 

 

Light diffusion is the scattering of direct light by making it pass through a non-transparent material or by bouncing it off a semi-reflective surface causing irregular reflection. 

 

6. Uses Of Optical Fibres?How does it work?

 


 

An optical fibre is a thin, flexible, transparent fibre that acts as a waveguide, or "light pipe", to transmit light between the two ends of the fibre to transmit signals over long distances , and used in fibre-optic communication to transmit information at a higher bandwidth and speed. It makes use of total internal reflection, when light is reflected in a medium.When light traveling in a dense medium hits a boundary at a larger,steeper angle than the "critical angle" for the boundary, the light will be totally reflected, this is used in optical fibres, to focus the light at the core and not let it go out of the medium.Here are the steps: 1. A ray of light is refracted into a long,glass block. 2. It hits the surface at a larger angle than the "critical angle" for the boundary, such that the light is not able to escape into the air but reflected back into the glass. 3. At the opposite face, it gets totally reflected again. 4. At the last surface, the light is refracted out again.

 

7. Explain optical density.

 


 

Optical density is the measure of the transmission of an optical medium for a given wavelength.Higher OD leads to lower transmittence,the higher protection factor by a filter and vice versa. For instance optical density of 1 means 90% of incident light is absorbed. 

 

(Continued in Main Page Part 2)

 

 

  

 

 

 

Comments (7)

hernyi said

at 11:58 am on Mar 2, 2011

i dont know what to do

ng yong sheng said

at 12:00 pm on Mar 2, 2011

read instructions. you supposed to do a write up on alternative energy sources and find out useful info about light (reflection, refraction, optical fibres, etc...)

ng yong sheng said

at 9:44 am on Mar 22, 2011

very well done. lots of revelant information. But you may wish to take out some information that you do not understand and not just copy and paste blindly.
You may want to take away some diagrams especially under the alternative energy section because they are all showing the same thing.

hernyi said

at 11:46 am on Mar 30, 2011

no its fangyi do one no plagraism he use "suo xie" technique

hernyi said

at 11:48 am on Mar 30, 2011

sorry stupid ivan cheong go do one

Lim Fang Yi said

at 12:56 pm on Apr 3, 2011

When I get computer access at 4pm I will finish the impact of the presence of plant on the temperature of the surrounding, how plants changes the temperature of the surrounding, how you can make use of the above to cool your home or building. I have added more information on the other renewable sources of energy.

Lim Fang Yi said

at 12:59 pm on Apr 3, 2011

it will be split into two parts due to large file size.(the main page)

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