Reflections

RE: Ecology

I feel that ecology is a topic is a very “free” topic. Unlike physics it does not have a specific theory for you to memorise. It is very free and the only way to score is to practice. By doing assessment books, you will have a better understanding of the topic. At first, I had difficulties understanding ecology as the range of knowledge is very wide. I was very nervous however, after consulting MS. Nada, she cleared some of my questions. My classmates also helped me, they thought me some of the basics. After knowing the basics, I manage to learn more on my self by researching on the internet. I started all of this very early so by the test I have a fully-compiled notes. I find ecology very interesting because most of it is about logical reasoning. 

IDS-Forensic Science

In term 3, during the sabbatical week, I went for an IDS course, where we learnt about forensic science. The course lasted four days, and we were exposed to many methods used to identify suspects, such as the length of the strides, fingerprint analysis, coding cracking and lip print analysis. We were also required to crack a murder case using two types of evidence, physical evidence and the evidence we got from suspects and eye witnesses. We formed groups of four and stayed with the group throughout the entire course, and we were required to make a presentation at the end of the course.

On the first day of the course, we were introduced to the crime and the evidence, as well as the programmes for the course and the schedule for the programmes. We were also given handouts that we were needed complete by the end of the course. We then proceeded to the labs to conduct experiments on our own, which was a very interesting and new experience, as lab lessons would normally be conducted after a teacher demonstrated, and we just follow. However, this time, we did not have much clue on how to do the experiments, and thus needed to figure out everything ourselves, which was tedious but yet at the same time, very meaningful, as we conducted the experiments by ourselves and learnt to be independent. One such experiment is figuring out how to crack a code, where we needed to try out many different methods of cracking before we cracked it. This is also is also more realistic as in the real world, we will not have any clue when we try to crack a code and will need to experiment with many different methods before finally solving the code. We were also given evidence of the crime scene such as blood smears and hair threads. When I first looked through the evidence, I was very confused with the murder case, as most of the evidence simply cannot give me any idea of how the murder happened. This makes the course even more exciting as it is just like a real murder case, where we need to figure out everything ourselves. However, after some careful reading and the Q&A session (a session where we can ask the suspects question, although their answers might not be real), I began to suspect Peter Hamilton.

On the second day, we had lab lessons, where we conducted many different experiments such as paper chromatography. We also had a session for us to brainstorm questions. From the Q&A session on day one, I can derive that more than one person was present at the crime scene with John lee (the victim). As a result, my questions on day two was mostly related to Peter Hamilton. However, the more I asked, the more confused I get. This is because the statements we got from the suspects and eye witnesses seem to contradict each other, and I had a very hard time distinguishing which evidence is reliable and which is not. At that point of time, I realised that solving a murder mystery was not as easy as it seems, and definitely much harder than the way it was portrait in CSI Miami. At one point of time, I actually thought of giving up and wait for the answers, but I quickly overcame that thought when I realised that it was quite fun to solve a crime bit by bit.

By the third day, I had a clearer picture of how and why the crime happened. The crime happened almost entirely due to dispute over money, and that Robyn Jones and Jane Liu are most likely innocent. However, one question always filled my mind, since the killer's height was 145 cm up till the arm, and the length of a human head is about 20cm, which adds up to 165cm, Peter Hamilton must not be the killer as he was about 180cm tall. However, he must be involved with the crime as what evidence points out. From this, I finally derived that he had an accomplice, but the question now will be, who?

On the last day, we finally figured out how the crime had happened and who was involved. However, the person that conducted the course, Mr Bill, gave us a lot of hints and guided us into solving the crime. I find that this was the result of one very serious problem, which is that we ask many irrelevant and unimportant questions, and do not think critically. As a result, Mr Bill needs to give us guide us on how to ask questions, before we actually solve it. I feel that I really need to improve on my questioning skills as I also asked some useless questions from the suspects, which not only does not give us a clearer picture, but also confuses us. We also had to make a presentation on what we had learnt, and the presentation is attached below. In conclusion, I feel that this course was very meaningful and I have benefited a lot from it. I hope that such courses can be held more frequently!

Term 3 test

Term 3 test was a stressful test to me because it is the test that decide the changes of me having an exemption for science. I need to get at least 34 to have a possibility of being exempted. I studied hard and I manage to obtain 38/40. I was very surprised and very delighted when I receive the marks. I felt relieved because it gave me a chance of being exempted. I think the few reasons for me achieving such a mark is because I did not do any last minute work this term, I was calm during the test and lastly I studied EVERYTHING this term.

I did not do any last minute work this term because I was accumalating the notes day by day. Hence by the day before test, I already have a word document with all the knowledge in it, hence all I need to do is to revise. This is very different from the past because what I did in the past is that I compile and revise during the few days before the exams.

I was calm during the test because I was fully-prepared. Normally during the test, I will be very nervous because I do not know what type of queations I will encounter but this term, I practiced and notice a trend in the questions. hence during the test, the questions were familiar and hence I was calm during the test.

Lastly I manage to revise everything before the test. Unlike term 2, I did not choose which subjects to study more, instead I decided to study everything. It is to ensure that I score a satisfying grade.

Hence I am very satisfied with this term’s result.

Lab Lesson in Term 3

The lab lessons in term 3 are much interesting, we get to play with lights. We learn the nature of light. We first use a piece of tool to produce a beam of light. Then we test the different experiments, learning what happen when a light enter a prism, cuboid and a sphere. At first I could not understand why the light acted in such a way but after consulting Ms. Nada she explained the different theories. I understood the nature of light afterwards. For this term’s lab lessons, its more on self-experiment, we have to try it out ourselves and learn the different theories ourselves. I find it more interesting when carrying out the expriment ourselves rather than reading it from the textbooks. Hence I definitely look forward to the different lab lessons.

Lab Lesson in Term 1

I feel that the lab lessons in term was rather interesting as we were able to test out the different the chemicals.

 When it comes to textbooks, all we can do is to picture the chemical in our mind, thinking how it will look like when one chemical react with another one. However, during lab lessons we do not need to picture anymore, everything is just observing. I think that it will help me understand better because I learn through visualizing the things. The experiments are very interesting. I feel that it is much more interesting than secondary one because this time we get to mix chemicals together. I still remember in sec one we only get to watch the videos from the internet but this year we manage to carry out the experiments ourselves.

The different mirrors

Summary (Light)

Light

What is light?

- Light is a form of energy

-It is non-matter

-Travels at a speed of 3 X 10⁸m/s

-Can be obtained either from a luminous source or being reflected from a non-luminous source

-A luminous source is something that produce light (e.g. Sun)

-It has both wave-particle and particle-like properties (wave-particle duality of light)

-Travels in a straight line

 

Reflection of Light

1. Incident Ray

- The ray of light that strikes the surface

Can be drawn:

- Dotted for virtual

- Solid line for real

2. Reflected Ray

- The ray of light that is reflected off a surface

Can be drawn:

- Dotted for virtual

- Solid line for real

3. Normal

- An imaginary line that is perpendicular to the surface at the point of incidence

Can be drawn:

- Dotted

4. The point of incidence

- The point where the incident ray strikes the surface

Can be marked with “O”

5. Angle of incidence

- Angle between the incident ray and the normal

Can be marked with “Angle i”

6. Angle of Reflection

Can be marked with “Angle r”

- Angle between the reflected ray and the normal

 

Laws of reflection

1^st Law

Incident Ray, Reflected Ray and the normal at the point of incidence all lie in the same plane.

2^nd Law

The angle of incidence is equal to the angle of incidence

Different Scenarios in Reflection

Scenario 1

(When surface is smooth and white)

-White light, containing 7 colours, is being reflected producing 7 colours reflecting in one single direction

  

Scenario 2

(When surface is smooth and coloured)

-If the surface is blue, only blue ray will be reflected, the rest of the seven colours will be reflected

  

Scenario 3

(When surface is smooth and black)

-No light will be reflected as the light ray will be absorbed by the black surface

 

Scenario 4

(When surface is rough and white)

-A single beam of light will split into many beams reflecting towards different directions

 

Scenario 5

(When surface strike on a rough and coloured)

 

Scenario 6

(When surface is rough and black)

-All the light will be absorbed, reflecting no light

 

Types of Reflection

-Diffused Reflection

Defined as light reflected from a smooth surface at a definite angle

-Specular Reflection

Produced by rough surfaces that tend to reflect light in all directions

 

Factors that will affect Reflection

-The type of reflected direction of the rays

-The type of surface

-The clarity of the reflected image

Image in a mirror

-Image is being form when light strikes a mirror and travels into your eyes

-Properties of the image on a plane mirror:

-Same size as the object

-As far behind the mirror as the object is in front of the mirror

-Same orientation as the object (upright or not)

-Laterally inverted

-Virtual

Virtual image cannot be captured on a screen because no actual light rays meet at the image position

 

Drawing Ray Diagram for Reflection

-Show Construction Lines (dotted)

-Label Diagram (angle of incidence, angle of reflection)

-Use straight line for any real things

-Use Dotted for any virtual things

-Use arrowhead to indicate the direction of a light ray

-Direction of the light must always be OBJECT --> MIRROR --> EYE

-To measure the angle of incidence and the angle of reflection, you need to:

-Construct Normal

-Measure using protractor

-Indicate angle on diagram

Total Internal Reflection

 

It is observed that all the light is reflected at the interface as if it had hit a mirror – a perfect mirror. This phenomenon is known as total internal reflection because 100% of the light is reflected within glass itself. There is no refraction at all. The light that is reflected follows the law of reflection such that the angle of incidence is equal to the angle of reflection.

In summary, total internal reflection occurs only when:

1) The incident ray is in the optically denser medium,

2) The angle of incidence is greater than the critical angle.

Critical Angle

Critical angle is defined as the angle of incidence in the optically denser medium when the angle of refraction in the optically less dense medium is 90 degrees.

The critical angle is different for different materials as it is dependent on the optical density of a material. A material with a greater optical density will have a smaller critical angle.

Optical Fibres

-Long thin strand of glass

-When a light ray is shone at one end of the fibre in such a way that it strikes the glass surface with an angle of incidence greater than the critical angle of the glass, total internal reflection occurs

-If the fibre were straight, the light ray will undergo multiple reflections and only emerge at the other end of it.

-The fibre usually has an outer plastic coating which helps to prevent the glass surface from being scratched.

-A damaged glass surface may allow light to escape through its side rather than at its end.

Applying internal Reflection

1) Optical Fibres in Telecommunication

Telecommunication is the transmission of information over long distances for the purpose of communication. Electromagnetic waves, light signals in optical fibres or electrical signals in copper wires are some ways in which information can be sent. In modern telecommunication, large volumes of information are transmitted daily via electronic devices such as the telephone, television, fax and the Internet.

 

How is information being sent in a basic telecommunication system?

A signal is firstly encoded on a laser beam. Light pulses (little bits of light) is then generated and sent along an optical fibre. Many different signals can be sent down the same optical fibre simultaneously. At the end of the fibre, a receiver unit detects the light pulses, decodes them and retrieves the information sent.

2) Optical Fibres in Endoscopy

An endoscope is an instrument used by doctors and surgeons to inspect or even perform medical operations inside a body. The endoscope can be inserted through a small hole made in the skin rather than a large cut.

 

An optical fibre endoscope is made up of a bundle of very thin optical fibres and lenses. Light enters the endoscope at the light guide connector, travels through an optical fibre bundle (i.e. the light fibre bundle), and exits to shine inside the body. Another optical fibre bundle (i.e. the image fibre bundle) collects the reflected light and carries the image to the lens at the control body. The image can be viewed on a monitor. Each of the thousands of fibres carries a small portion of the image and any black dot on the image represents one broken fibre.

3) Prisms

When a light ray enters along a normal as shown in the above diagram, it strikes a slant surface at an angle of incidence of 45º. The critical angle of glass in air is typically 42^o. Hence, the light ray undergoes total internal reflection as its angle of incidence is greater than the critical angle of glass. The light ray then emerges from the prism along a normal. In this way, the light ray is turned through 90º with one total internal reflection.

 

Two right-angled prisms can be arranged as shown in the diagram below to form a periscope. A periscope may be used by people in a submarine to see above the sea surface or to see over the heads of people in a crowd.