Monday, September 26, 2011

Registration for Singapore Amazing Flying Machine Competition 2012

Dear all,

If you are interested to join the Singpaore Amazing Flying Machine Competition 2012,
Please look register at the following URL http://tiny.cc/safmc2012.

If you would like to clarify any doubts do look for Mr Tan HT.
Thanks.

Monday, August 22, 2011

Level Test for Science on 24 August 2011 (Wednesday)

Topics to be tested:
Reflection
Refraction
Sound (Concepts learn in General Wave Properties is needed.)

Duration: 1h
Test Structure:
MCQ - 10 marks
Short Structure Question - 25 marks
Long Question - 10 marks
Total: 45 marks

Things to bring:
Writing materials including pencil
Calculator
Protractor
Ruler

Saturday, August 6, 2011

Applications of total internal reflections

Optical Fibers are made of silica and use total internal reflection to act as a guide for the light waves, therefore being more efficient than metal, having less loss and being immune to electromagnetic interference. The core is made of a transparent material, and is surrounded by a material with a lower refractive index. This allows total internal refraction to occur.

Prismatic Binoculars use prisms to direct light and utilise total internal reflection to prevent light loss from bouncing around in the binoculars itself.

Fingerprinting Devices use Frustrated Total Internal Reflection to map out the impression left by the friction ridges on our fingers.

The Rain sensor uses an infrared beam and shoots it at the windscreen at 45º angle. If the windscreen is wet, less light will return to the sensor.

Tan Siah Wei

Tuesday, August 2, 2011

Applicants of Total Internal Refletion ( Brendon Goh )

Uses of Total Internal Reflection


  1. Optical Fibers:


It is the maximum angle from the fiber axis where light enters the fiber and will propagate, or travel, in the core of the fiber. The sine of this angle is the numerical aperture (NA) of the fiber. Fiber with a larger NA needs less precision to splice and work with than fiber with a smaller NA. Single-mode fiber has a small NA.


  1. Rain Sensors:


The most common modern rain sensors are based on the principle of total internal reflection: an infrared light is beamed at a 45-degree angle into the windshield from the interior — if the glass is wet, less light makes it back to the sensor, and the wipers turn on. Most vehicles with this feature have an "AUTO" position on the stalk.


  1. Fingerprint Detection:


The Frustrated Total Internal Reflection (FTIR) is the most used and mature live-scan sensing technique. The finger is illuminated from one side of a glass prism with a LED, while the other side transmits the image through a lens to a CDD/CMOS sensing element which converts light into digital information. The lack of reflection caused by the presence of water particles where the ridges touches the prism allows ridges to be discriminated from valleys.



Sources:

http://en.wikipedia.org/wiki/Total_internal_reflection

http://en.wikipedia.org/wiki/Optical_fiber

http://en.wikipedia.org/wiki/Rain_sensor#Automotive_sensors

http://www.casscountynd.gov/county/depts/sheriff/corrections/Pages/Fingerprints.aspx


Done By:


Brendon Goh




Monday, August 1, 2011

Application of Total Internal Reflection

1. Fingerprinting devices
Fingerprinting devices use frustrated internal reflection in order to record an image of a person's fingerprint without the use of ink.











2. Rain sensors
An infrared light is beamed at a 45-degree angle into the windshield from the interior — if the glass is wet, less light makes it back to the sensor, and the wipers turn on.


























3. Ability of diamonds to sparkle
Most rays entering the top of the diamond will internally reflect until they reach the top face of the diamond where they exit.






























4. Optical Fibres
A fiber optic is a glass "hair" which is so thin that once light enters one end, it can never strike the inside walls at less than the critical angle. The light undergoes total internal reflection each time it strikes the wall.   Only when it reaches the other end is it allowed to exit the fiber. Fiber optic cables are used to carry telephone and computer communications.
Advantages-->
Fiber optics can carry much more information in a much smaller cable. 
No interference from electromagnet fields result in "clearer" connections.
No electrical resistance.
No hazard of electrocution if cable breaks.




Applications of Total Internal Reflection by Izzat and Joel

Applications:

1. To make diamonds sparkle

- The cut of the diamond favors total internal reflection. Most rays entering the top of the diamond will internally reflect until they reach the top of the face of the diamond where they exit. This gives diamonds their bright sparkle and hence, look more attractive.

2. To make information travel rapidly on light waves through a fiber optic

- A fiber optic is a glass "hair" which is so thin that once light enters one end, it can never strike the inside walls at less than the critical angle. The light undergoes total internal reflection each time it strikes the wall. Only when it reaches the other end is it allowed to exit the fiber.

- Fiber optic cables are used to carry telephone and computer communications. Advantages over electrical wired include:

  1. Fiber optics can carry much more information in a much smaller cable.
  2. No interference from electromagnet fields result in "clearer" connections.
  3. No electrical resistance.
  4. No hazard of electrocution if cable breaks.
3. Prismatic binoculars

- Uses the principle of total internal reflections to get a very clear image

4. Automative rain sensors

- The most common modern rain sensors are based on the principle of total internal reflection: an infrared light is beamed at a 45-degree angle into the windshield from the interior. If the glass is wet, less light makes it back to the sensor, and the wipers turn on. Most vehicles with this feature have an "AUTO" position on the stalk.

5. Flashlight lensesPrecision-molded TIR lens for the X200A.
- The X200A LED Handgun WeaponLight uses a total internal reflection (TIR) lens that is precision molded from a special cyclo-olefin polymer. The lens surrounds the LED, gathering virtually all of its light, which it reflects and refracts forward in an exceptionally tight beam that cannot be duplicated with a reflector.







Sources:
- http://www.surefire.com/why_surefire#Lenses
- http://en.wikipedia.org/wiki/Total_internal_reflection#Applications
- http://en.wikipedia.org/wiki/Rain_sensor#Automotive_sensors
- http://en.wikipedia.org/wiki/Binoculars#Prism_binoculars
- http://regentsprep.org/Regents/physics/phys04/captotint/default.htm

Research on Applications of Total Internal Reflection (TIR)

These are the Uses and Applications of Total Internal Reflection that I had researched on:

1) Can be used to make diamonds sparkle (because of the reflection then we can see the diamond sparkle)

- The cut or shape of a diamond is nicely 'suited' for total internal reflection. Light Rays which enter the diamond from one of its 5 sides (for a 2D Shape Diamond) will therefore be nicely reflected back out from the same side which they entered the diamond. There will hence not be any refracted ray when a light ray enters a diamond, basically due to its shape. What causes the diamond to sparkle is the way the light ray enters and leaves the diamonds, where they will enter and leave from the same side of the diamond. 

2) Can be used to let information travel rapidly on light waves through a fiber optic

- A fiber optic is a glass 'hair' which is so thin that once light enters it from one end, it can never strike the inside walls less than the critical angle. Therefore, the light rays will have to undergo total internal reflection in the fiber optics each time it strikes the walls in them, before it actually exits the fiber when it reaches the other end. Fibre optic cables are used to carry telephone and computer communications. This is why total internal reflection is so important, because it helps us to be able to communicate with others.

3) Will Occur in Deserts on Hot Summer Days. Mirage is an optical illusion.

- In deserts, the temperature of air near the earth is maximum and hence is rarer or lighter. The upper layers of air, which is cooler, will be denser. A ray of light from the top of a tree in the desert will travel from denser air to rarer air and eventually bend away from the normal. At a particular layer, if the angle of incidence were to be greater than the critical angle, then total internal reflection will occur. Thus, the inverted image of this tree will create an optical illusion of reflection from a pond of water. Having total internal reflection is also why we are able to see the reflection of a tree in a pond of water in deserts.

Sources: http://regentsprep.org/Regents/physics/phys04/captotint/default.htm
http://www.tutorvista.com/content/physics/physics-iv/optics/total-internal-reflection.php 

Done By: Tan Hao Ming (18)

Friday, July 22, 2011

Level Test for Science on 28 July 2011 (Thursday)

Topics to be tested:
General wave properties
Electromagnetic Spectrum
Reflection

Duration: 1h

Test Structure:
MCQ - 10 marks
Short Structure Question - 25 marks
Long Question - 10 marks
Total: 45 marks

Things to bring:
Writing materials including pencil

Calculator
Protractor
Ruler

Saturday, July 9, 2011

microwaves (Daniel Tan, Wan Ray Chow, Ong Ding Shan, Chan Jia Ler

Microwaves are basically extremely high frequency radio waves, and are made by various types of transmitter.

Microwaves have wavelengths that can be measured in centimeters! The longer microwaves, those closer to a foot in length, are the waves which heat our food in a microwave oven.


Their wavelength is usually a couple of centimetres. Stars also give off microwaves.

Microwaves cause water and fat molecules to vibrate, which makes the substances hot.

That is why we should not put certain food substances such as eggs into microwaves as the egg shells of eggs do not contain water and fat molecules while the yolk and white contains these molecules and therefore if we put an egg into microwaves the white and yolk would expand and therefore cause the egg to explode from the inside.


Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke.

These qualities make them able to be used in speed cameras and radars


Prolonged exposure to microwaves is known to cause "cataracts" in your eyes, which is a clouding of the lens, preventing you from seeing clearly. We should also never put aluminum foil inside microwaves as . When the strong microwaves produced by a microwave oven interact with a sheet of aluminum foil, their electric fields cause the mobile electrons in the foil to accumulate at the sheet’s sharp, pointed tips. This build-up of electrons creates a strong electric field in the surrounding air.

When the electric field becomes strong enough, it causes free electrons in the air to accelerate and jar loose more electrons from gas molecules in the air, which then go on to jar even more electrons loose. This chain reaction creates an electrical charge in the air, which shows itself as sparks. Although rounded metal objects such as spoons are less likely to create sparks, the safest bet is to avoid putting any kind of metal in the microwave.


sources:http://www.darvill.clara.net/emag/emagmicro.htm

http://cfbt-us.com/wordpress/wp-content/uploads/2010/04/wavelength_lr.jpg

http://indianapublicmedia.org/amomentofscience/metal-in-the-microwave/

Tuesday, July 5, 2011

Ultraviolet Waves ( Mathias, Brendon, Jin Qian, Bevan )

Ultraviolet waves




Usage: optical sensors, disinfection, forensic analysis, drug detection, medical image of cells.


Usage: Detecting Counterfeit Money

UV counterfeit detectors feature a light that makes anti-counterfeiting measures in a bill light up and appear yellowish-green. Machines with MG detectors detect magnetic ink that is in the currency. When a bill is slid over the detector, the machine will let you know if it is authentic or fake. Some detectors even include a built-in light that makes it easier to see printed watermarks.



Beneficial: One of the beneficial uses of UV light are that it can be used to kill bacteria and other microbes. It is commonly used to purify water for instance or clean things. UV waves have other applications in life, such as black lights. Also many compounds fluoresce (they emit light) when exposed to UV light. Forensic scientist uses UV light to look for blood or body fluids. Finally exposure to some UV light causes the body to make Vitamin D, an important nutrient for the body. Although UV light is important, too much will cause sunburns and possibly cancer.


Unique features of Singapore currency to prevent Forgery:

Portrait Watermark

A three-dimensional multi-tone portrait watermark of the late Mr Yusof bin Ishak can be seen when viewed against transmitted light. The watermark has a three-dimensional appearance with areas in varying tones of dark and light.

Highlight Watermark

This monotone watermark is located below the Portrait watermark on the front of the note. It corresponds with the Braille pattern at the top right-hand corner of each denomination. The primary characteristic of the Highlight Watermark is that its extra thin area makes it appear clear and distinct when the note is held against light.




Dangerous: Sunburn, Skin cancer Skin diseases


Description:

wavelength shorter than visible light, longer than x - rays

Violet in colour






Sources:

http://www.howtodothings.com/business/how-to-detect-counterfeit-money

http://wiki.answers.com/Q/What_are_the_advantages_and_disadvantages_of_UV_or_ultraviolet_light#ixzz1RCbfAMWB

http://www.mas.gov.sg/currency/currency_info/notes/Singapore_Circulation_Notes_Distinguishing_Counterfeit_Notes.html

http://en.wikipedia.org/wiki/Ultraviolet




Done by Matthias lee, Yu Jin Qian, Brendon Goh, Bevan koo

Infrared (Hao Ming, Siah Wei and Mikhael)

Effects of Infrared Waves
1) It may cause damage to the eyes and vision.
2) Generates heat and radiation.
Uses of Infrared Waves
1) Night Vision
Operates through the conversion of ambient light photons into electrons which are amplified by a chemical and electrical process which converts it into visible light.
2) Thermography
Infrared can be used to determine the temperature of objects. With it, we are able to see the temperature through the change in the colours. If the object is too hot in the NIV, using infrared to determine its temperature through the colours will be termed pyrometry. 
3) Communication
Infrared can be used to send data from a part of the earth to another. They are found in computers which are commonly used for communication. Infrared are also found in the remote controls of televisions and also radios, and many other forms of communication.

4) Astronomy
Some telescopes contain infrared and these type of telescopes are used by scientists or astronomers to observe objects in the infrared portion of the electromagnetic spectrum using optical components, including mirrors, lenses and solid state digital detectors. 
5) Climatology
In climatology, which is referring to the study of climate change, atmospheric infrared radiation is used to detect trends in the energy exchange between the Earth and the atmosphere. These trends will provide people with information about the long term changes in the Earth’s climate, and therefore they are able to provide a conclusion on it.

The picture on the left which we have is about the changes in colour as temperature changes. As mentioned before in Point 2 of the uses of infrared waves, infrared can also be used to determine the temperature of different objects. This point also mentioned about the colour changes due to the differences  in the temperatures. This picture on the left exactly shows the colours which will appear or be revealed due to the different temperatures. For example, as shown in the picture, when the temperature of an object is 140D”F, the colour which appeared or which is being revealed will be light red. Then, when the temperature of another object is 20D”F, the colour which appeared or which is being revealed will become dark purple. This is something like the pH in Chemistry. And, when we look at the temperature of boiling water, the colour which appeared or which is being revealed will become light green. (The temperature of boiling water is 100ºC or 100D”F) 


A picture showing the comparison between the looks of visible light and infrared. This are the looks of the two type of lights, or rather how they will appear when the night vision goggles are put on. The difference between the visible light and the infrared is that infrared  is a low level light that is emitted by objects too cool to radiate visible light. The picture below now shows a summary of all the 7 types of waves (including infrared):



Our Sources and Acknowledgements (for the research, information and pictures):
http://en.wikipedia.org/wiki/Infrared#Night_vision  
http://4.bp.blogspot.com/__-SLJp2JFNE/TGabqHczNjI/AAAAAAAAAC4/SpjS4I5-S8o/s1600/14167-1.jpg (for the picture on the colour changes as temperature changes)

Gama Rays


-Has enough energy to damage body cells 
-Is given off from stars or radioactive substances
-Is used to kill cancerous cells by targeting rapidly dividing cells
-Can cause cell damage and can cause a variety of cancers.   (May cause mutation in cells

Done by Abram, Abu, Mingyong and Chen Yu 

Radio Waves (Akhil, Heo Yub, Jake, Jonathan)



- Radio waves are made by various types of transmitters.
- Natural radio waves are caused by lightning, stars, sparks which is why there is an interference on the radio when there is a thunderstorm.
- Radio waves can reflect off the ionosphere (part of the upper most layer of the ozone layer) to travel around the earth.
- Radio frequency is used for medical usage, for minimally invasive surgery, like sleep apnea.

Four types of waves
- Long waves: around 1-2km in wavelength used to broadcast over long distances like in the united states from state to state.
- Medium waves: around 100m in wave length , usually used in AM stations
- VHF(Very High Frequency): around 2m in wavelength. FM radio stations in civilian aircrafts and taxis.
- UHF(Ultra High Frequency): wavelengths of less than a meter. Used for police radio communications, television transmissions and military aircraft radios.

FM vs AM Radio
-AM Waves are easily affected by weather and large objects between the radio receiver and transmitter.
-FM Waves are not very easily affected by weather.
-AM waves are preferred for transmitting over long distances as it follows the curvature of the Earth. FM waves travel in straight lines so are not that suitable for transmitting over longer distances

X-Rays & Visible Light (Omnoms)


X-Ray
  • Emitted when an electron moves from certain excited states back down to its ground states, or when an electron that is moving very quickly is suddenly stopped.
  • Two groups - long wavelength (soft x-rays) and shorter wavelength (hard x-rays)
  • Used for radiography (x-ray photography) and to look at materials in industry for defects.
  • Dangers of using on humans: Skin diseases and cancers
Visible light
  • Colours of the rainbow:
  • Red (Longest Wavelength, Lowest Frequency)
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet (Shortest Wavelength, Highest Frequency)
  • Used for communications (fiber optics - transmits light between the two ends of the fiber)
  • Dangers: Too much light can damage the retina of your eyes



(Fun Fact:An easy way to remember the colours of the rainbow: Richard Of York Gave Battle In Vein )

Thursday, June 30, 2011

Example 3 (Jake and Jonathan)


a) 90/1.55
=58.1cm/s (to 3s.f.)

b) It is possible to change the speed when the tension is changed.

Wednesday, June 29, 2011

Wave Pulse (Akhil & Bevan)

a)
Speed
=Distance/Time
=90/1.55
=58.1cm/s


b) It is possible to change the speed of the wave pulse by changing the tension of the rope.

MingYong, Abu and Abram's Answer for example 3

(a)Speed of the wave pulse-90/1.69=53.33=0.533m/s(to3s.f.)


(b)By changing the tension, the speed of the wave pulse is affected.

Example 3 ( Brendon and Hao Ming )

Here is the screen shot for the Example 3, the pulse travelled 90 cm in 1.69 seconds. 

From here, we calculated the speed of the wave pulse. 
Using the formula of S = D/T, the speed is equal to 90/1.69 = 53.3 cm/s, to 3 s.f. 




For the next part, it is actually possible to change the speed of the wave pulse by changing the tension to 'low'.

This cause the time to get 17.02 seconds, longer than the 1.69 seconds. The new speed is equal to 90/17.02 = 2.59 cm/s to 3 s.f. 





Thank you. Done by: Hao Ming and Brendon Goh (S2 - 06)

Example 3

(a)53.3m/s
(b)Only when the tension is changed, the speed decreases while maintaining the same width. Changing the amplitude does not affect the speed.



Done by: Ding Shan, Joel and Izzat

a)v=90/1.52
v=59.2cm/s
=0.592m/s

b)Yes,when the tension is higher,the speed of the wave is higher

Wave simulation evidence (Siah Wei and Chen Yu)














As clearly shown in the two pictures...with the same settings for amplitude, pulse width and damping...by changing the tension from high to low..the speed decreases.