Monday, October 3, 2011
Friday, August 5, 2011
Please get the following completed.
Name / ID (Register Number) /Class
Remember to submit your homework.
Wednesday, August 3, 2011
Total Internal Reflection in real life
One way to observe it is while swimming, if one opens their eyes just under the water's surface when the water is calm, the water surface will appear mirror-like.
In addition, it is observed when we critically cut diamond. This is what gives it maximum sparkle.
Fourth way would be in fingerprinting devices, which uses total internal reflection in order to record an image of a person's fingerprint without the use of ink.
A final way would be on a prismatic binoculars which uses the principle of total internal reflections to get a very clear image.
Tuesday, August 2, 2011
Application of Total Internal Reflection:
- Fibre Optics uses in telecommunications:
There are two types of optical fibre used in telecommunications which are the step-index fibre and the graded-index fibre. The step-index fibre is in which the core is made from one type of glass while the outer cladding has a lower refractive index. The graded-index fibre is when the refractive index of the material gradually decreases outwards from the centre of the fibre.
Before optical fibres were invented, telecommunications used copper cables. Some of the problems that people faced while using the copper cables are that due to the copper’s resistance which changed some energy into heat, signals were reduced and had to be re-amplified every few kilometres.
Advantages: Fibre optics used in telecommunications are far more efficient, less bulky and much cheaper. Some examples are local area networks, cable tv and CCTV.
- Astronomy; the study of stars and galaxies
Fibre optics are used if several stars and galaxies needs to be studied simultaneously to analyse red-shift or spectra. They are bundled together and placed at the focus of a telescope in a block. Hence, each optical fibre received light from parts of the image of the sky.
Advantages: The fibres will lead the light to an instrument where it can studied by translating the light into an electrical signal and feeding the collected data into a computer.
- Endoscope or Fibroscope:
An endoscope is any instrument used to look inside the body. Thousands of optical fibres are bundled together in an endoscope which is inserted into a human body so that the doctor can 'see' inside. Light can be directed down the fibres even if they are bent, allowing the surgeon to illuminate the area under observation. He can then view this from a television camera linked to a monitor by coherent fibres. Endoscopes are widely used both in medical and vetenary practices. The physics principle on which they are based is total internal reflection within a fibre optic bundle of fibres.
Advantages: Endoscopes can be used to explore and biopsy such areas as the colon and the bronchi of the lungs. By employing miniature television cameras and tiny surgical implements that allow not only exploration but also endoscopic surgery. Through small incisions; such surgery is much less traumatic to the patient than traditional open surgery. Recovery times are shorter, and less anaesthetic is required.
- Bicycle reflectors
- Binoculars/ Periscopes
- Cutting/carving of the diamonds
Monday, August 1, 2011
rain sensors, which can be used for automatic windscreens
filtering of light for light sensor wiring
prismatic binoculars uses total internal reflections uses the principle for a higher quality image
Friday, July 22, 2011
Please note that the powerpoint slides and additional practice questions are up.
Tuesday, July 19, 2011
Tuesday, July 12, 2011
B) There is a good video that will give you an introduction on reflection.
C) Complete section 1.2.
1) Go through the simulation
2) Through your observation, identify the 5 properties of image formed by mirror.
D) Take 10mins and complete the pre-quiz on the topic
Get it done please..
Friday, July 8, 2011
Among all electromagnetic waves, gamma rays have the shortest wavelengths (less than 0.01 nm), highest frequencies (around 1019 Hz), and, consequently, the highest energies (at least 100 keV). They’re even more energetic compared to their more popular cousins, X-rays. Hence, gamma rays have the smallest wavelengths and the most energy of any other wave in the electromagnetic spectrum. These waves are generated by radioactive atoms and in nuclear explosions. Gamma-rays can kill living cells such as using gamma-rays to kill cancerous cells.
Gamma-rays travel to us across vast distances of the universe, only to be absorbed by the Earth's atmosphere. Different wavelengths of light penetrate the Earth's atmosphere to different depths. Instruments aboard high-altitude balloons and satellites like the Compton Observatory provide our only view of the gamma-ray sky.
Gamma-rays are the most energetic form of light and are produced by the hottest regions of the universe. They are also produced by such violent events as supernova explosions or the destruction of atoms, and by less dramatic events, such as the decay of radioactive material in space. Things like supernova explosions (the way massive stars die), neutron stars and pulsars, and black holes are all sources of celestial gamma-rays.
This is because most of the gamma radiation observed on the surface of the Earth come from radioactive substances. Due to the wave-particle duality of matter, gamma rays (which are actually electromagnetic waves) are also known as gamma particles. These particles, released during a transition of a radioactive nucleus from a more excited state to a lesser one, bear the energy difference between the two states.
These energy differences are very large, typical of the energies exhibited during interactions in the nucleus. As a consequence, the gamma particles carrying this released energy are very much capable of wreaking havoc on atoms they collide with, rendering the atoms ionized. Thus, like X-rays, gamma rays are considered ionizing radiation.
Gamma particles are actually photons. That means they have zero mass. Despite this, they carry a lot of momentum. Classical physics tells us that this cannot be possible. However, because of the extremely high speeds that these gamma particles have the moment they are released from the nucleus, relativistic effects have to be considered.
One consequence of which is the ability to acquire momentum despite having zero mass. That is why these massless gamma particles can still collide and dislodge loosely attached atom members like electrons. This is precisely the reason why gamma rays, like X-rays, are harmful to the body. Gamma rays can be stopped by high density shielding materials like lead.
Other than for astronomy ,they are used to kill cancer cells without having to resort to difficult surgery. This is so as Gamma rays can kill all living cells.This is called "Radiotherapy", and works because cancer cells can't repair themselves like healthy cells can when damaged by gamma rays.
There's also targeted radiotherapy, where a radioactive substance is used to kill cancer cells - but it's a substance that'll be taken up by a specific part of the body, so the rest of the body only gets a low dose. An example would be using radioactive iodine to treat cancer in the thyroid gland.
Radioactivity is particularly damaging to rapidly dividing cells, such as cancer cells. This also explains why damage is done by radiotherapy to other rapidly dividing cells in the body such as the stomach lining (hence nausea), hair follicles (hair tends to fall out), and a growing foetus (not because of mutations, but simply major damage to the baby's rapidly dividing cells).
Gamma rays are also used to sterilise medical equipment and killed microbes in food so that it will last longer.
Infrared is easily generated and doesn't suffer electromagnetic interference, so it is nicely used to communication and control. Some other light emissions could contain infrared as well, and that can interfere in this communication. The sun is an example, since it emits a wide spectrum or radiation.
Infrared Photography is another aspect of infrared. infrared (IR) light pass through to the camera, while all or most of the visible light spectrum are being blocked.
They travel in waves. Ultraviolet radiation is more energetic than visible radiation and therefore has a shorter wavelength. To be more specific: Ultraviolet rays have a wavelengthbetween approximately 100 nanometers and 400 nanometers whereas visible radiation includes wavelengths between 400 and 780 nanometers.
The major source of this rays is the Sun mainly. 99% of the Sun’s rays are in the form of visible light, ultraviolet rays, and infrared rays (also known as heat). Light enables us to see, and heat keeps us from being cold. However, ultraviolet rays often carry the unfortunate circumstance of containing too much energy. The energy contained in ultraviolet rays is higher, so instead of just causing the molecules to shake, it actually can knock electrons away from the atoms, or causes molecules to split. This results in a change in the chemical structure of the molecule. This change is especially detrimental to living organisms, as it can cause cell damage and deformities by actually mutating its genetic code.
Ultraviolet rays can be subdivided into three different wavelength bands, UV-A, UV-B and UV-C. They are classified on the amount of energy they contain and their effects on biological matter, ranging from UV-C to UV-A, from the most energetic and harmful to the least energetic and harmful.
Thankfully, the UV-C rays are blocked from the Earth’s Surface thanks to the presence of the Ozone Layer which breaks apart the bond of the molecule and absorb the energy. UV-B rays and UV-A have a lower energy level, thus longer wavelength, insufficient enough to split an ozone molecule, some extending down to the Earth’s Surface. Both UV-B and A are detrimental to health, particularly between the hours of 11am and 3pm.
Documentary on UV rays
A microwave oven passes (non-ionizing) microwave radiation (at a frequency near 2.45 GHz) through food, causing dielectric heating by absorption of energy in the water, fats, and sugar contained in the food. Microwave ovens became common kitchen appliances in Western countries in the late 1970s, following development of inexpensive cavity magnetrons. Water in the liquid state possesses many molecular interactions which broaden the absorption peak. In the vapor phase, isolated water molecules absorb at around 22 GHz, almost ten times the frequency of the microwave oven.''
Microwaves also cause microwave burns which are caused by ionizing radiation being abosorbed into organisms(us). they manifest slowly and will show greater signs over a longer period of time,causing major tissue damage if greatly exposed.
the first electromagnetic experiments conducted by Heinrich Hertz in 1886 and also by Marconi used frequencies near the microwave region - some around 500 MHz and some even in the multiple GHz (Gigahertz) region
Justin is a pop fag
- When the wavelengths of light decrease, X-Rays increase in energy
- Smaller wavelengths, and thus have higher energy compared to ultraviolet waves
- X-ray detectors collect photons of X-ray light
- Due to Earth’s thick atmosphere, no X-rays are able to penetrate from outer space to Earth’s surface
- X-rays cannot be felt by us
- Because bones are dense and absorb more X-rays compared to the skin, silhouette of the bones are left on he X-ray film while the skin appears transparent.
- Things in space that emits X-rays, which include black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun and some comets.
Wednesday, July 6, 2011
Complete the 2 excerise below:
1) Go through the following simulation on EM spectrum.
2) Watch the video to understand more about the spectrum
Tuesday, February 15, 2011
1. http://www.enchantedlearning.com/subjects/plants/leaf/ (Online Readings)
Sunday, January 16, 2011
Friday, January 14, 2011
Wednesday, January 12, 2011
Tuesday, January 11, 2011
The variety of different lives on Earth.
#2. In one or two sentences, explain why biodiversity is important to us.
It provides us with a variety of natural resources such as food. It also balances the ecosystem.
#3. What is the key understanding of this lesson?"
I have learnt how to clearly classify the different types of lives into the 5 different kingdoms.
Khim Tan (05)
Biodiversity is the variability of all living organisms (including animal and plant species) of the genes of all these organisms, and the terrestrial, aquatic and marine ecosystems.
In one or two sentences, explain why biodiversity is important to us.
With every breath we take, we consume oxygen produced by forests and seas. Every mouthful of food has been living material that relied on soil, microbes and plants to grow thus it provides us with the basics of life.
What is the key understanding of this lesson?
All living things of Earth used to be on its own but slowly it is being classified by the different kingdoms of life from 2 basic kingdoms of Plantae and Animalia till now the 5 Kingdoms, Animalia, Plantae, Monera, Protista and Fungi.
Looi Wei Chern (15)
Biodiversity is the variation of life forms within a given ecosystem or an entire planet.
In one or two sentences, explain why biodiversity is important to us.
It is important as it helps to balance the ecosystem like the food chain as without the prey, the predator would soon become extinct
What is the key understanding this lesson?
The key understanding was of how and which groups the different organisms were classified into no matter how similar they looked like to another group. I also learned a little bit about the different groups.
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet.
2. In one or two sentences, explain why biodiversity is important to us.
Biodiversity brings enormous benefits to mankind from direct harvesting of plants and animals for food, medicine, fuel, construction materials, and other uses to aesthetic, cultural, recreational and research values.
3. What is the key understanding of this lesson?
We have learnt how the classify the creatures of the world into five different kingdoms
Azeem Arshad Vasanwala
Biodiversity is important as without it, there will be an imbalance in the ecosystem and it ensures the continuity of one's kind so that it will not become extinct, basically, to ensure the continuation of the food chain or web.
I have learnt the different kingdoms and how to classify them based on the different levels of taxanomy. I have also learnt on how they are classified based on their structural characteristics and behavioural characteristics. Besides that, i have learnt on scientific name came about and how to write it correctly.
Monday, January 10, 2011
Monera are about 1 micrometer in size and complex as living molecules. An example of Monera are bacteria. The cell structure of Monera lacks nuclei and many other organelles.
The source of nutrition for these organisms is usually photosynthesis or chemosynthesis.
The Monera characteristics also include the shape of the cell that includes round (cocci), rod-like (bacilli) or spiral (spirochetes or spirilla).Monera reproduce asexually through binary fission or sexually by conjugation. The process of circulation and digestion is carried out through diffusion.Most of the Monorans can survive harsh environment by producing spore coa.
Sunday, January 9, 2011
Myriapoda consist of millipedes, centipedes and others. Although their name suggests they have myriad (10,000) legs, they range from having over 750 legs to having fewer than ten legs. Myriapods have a single pair of antennae and, in most cases, simple eyes. The mouthparts lie on the underside of the head, with an "epistome" and labrum forming the upper lip, and a pair of maxillae forming the lower lip. Myriapods breathe through spiracles that connect to a tracheal system similar to that of insects.
Reptiles fall under the Class Reptilia. They are separated by 4 orders:Crocodillia(the crocodylians) the Sphenodonta (tuatara), Squamata(lizards and snakes) and Chelonia(turtles). Most reptiles have scales,have lungs to breathe and are all cold-blooded.They also lay eggs to reproduce,although certain species do give birth to young alive.The reptile eggs and most of the times buried underground to wait for it to hatch.They are all vertebrates which means they have backbones.
Saturday, January 8, 2011
Friday, January 7, 2011
Echinoderms (Phylum Echinodermata) are a phylum of marine animals.The phylum contains about 7,000 living species including sea cucumbers, sea urchins and starfish. The echinoderms are important both biologically and geologically: biologically because few other groupings are so abundant in the biotic desert of the deep sea, as well as the shallower oceans, and geologically as their ossified skeletons are major contributors to many limestone formations, and can provide valuable clues as to the geological environment. Many echinoderms have remarkable powers of regeneration. Some starfish are capable of regenerating lost arms. In some cases, lost arms have been observed to regenerate a second complete sea star. Sea cucumbers often discharge parts of their internal organs if they perceive danger. The discharged organs and tissues are quickly regenerated. Sea urchins are constantly losing their spines through damage — all parts are replaceable. Some starfish populations can reproduce entirely asexually purely by the shedding of arms for long periods of time.
Insectas have a chitinous exoskeleton, a three-part body (head, thorax, and abdomen), three pairs of jointed legs, compound eyes, and two antennae. They are one of the most diverse group of animals on the planet and include more than a million species and represent more than half of all known living organisms. Insects move about by walking, flying or occasionally sinking and swimming at the same time.
picture taken from:http://en.wikipedia.org/wiki/Insect
- A frond is the leaf of the fern
- Fronds attached to a rhizome(specialized, root-like stem) by a stalk(aka stipe)
- Can grow till ≥ 18m in height and have leaves ≥ 5m long
- Reproduce by spores
- Usually found in trees
Characteristics of Cnidaria(Animalia)
1) Radially Symmetrical.
2)Body multicellular, few tissues, some organelles.
3)Body contains an internal cavity and a mouth.
4)Two different forms exist, medusa and polyp
5)Reproduction is asexual or sexual.
6)Has a simple net like nervous system.
7)Has a distinct larval stage which is planktonic.
8)Lives in aquatic environments, mostly marine.
9)Mostly carnivorous otherwise filter feeders.
10)May have a minimal skeleton of chiton or calcium carbonate.