2011 S2-06 Science Blog
Monday, September 26, 2011
Registration for Singapore Amazing Flying Machine Competition 2012
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.
Tuesday, August 23, 2011
Monday, August 22, 2011
Level Test for Science on 24 August 2011 (Wednesday)
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
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 45ยบ 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
- 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.
- 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.
- 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
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
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:
- 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.
- 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 lenses
- 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)
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)
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 )
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://en.wikipedia.org/wiki/Ultraviolet
Done by Matthias lee, Yu Jin Qian, Brendon Goh, Bevan koo
Infrared (Hao Ming, Siah Wei and Mikhael)
Gama Rays
Radio Waves (Akhil, Heo Yub, Jake, Jonathan)
- Radio waves are made by various types of transmitters.
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
- 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
Thursday, June 30, 2011
Wednesday, June 29, 2011
Wave Pulse (Akhil & Bevan)
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
(b)By changing the tension, the speed of the wave pulse is affected.
Example 3 ( Brendon and Hao Ming )
Thank you. Done by: Hao Ming and Brendon Goh (S2 - 06)
Example 3
(b)Only when the tension is changed, the speed decreases while maintaining the same width. Changing the amplitude does not affect the speed.