Experiment 4- Behaviour of Beta particles in a magnetic field

The purpose of this experiment was to determine whether the radioactive decay from a radioactive source, Radium-226, emits electrons or positrons. Positrons are the positively charges anti-particles of negatively charged electrons. We used the fact that they are oppositely charged to determine which type of beta decay Radium-226 emits. In the presence of a magnetic field, the moving charged particles would be deflected away from an otherwise straight path. The experimental set-up was designed such that if the particles were electrons, they would be deflected to the right if they are electrons and to the left if they are positrons.

From our experimental results we learned that the when the radioactive source was placed in front of the magnetic field, the Geiger counter registered higher counts towards the right of the set up, this showed that, by Fleming’s law of induction, the emitted particles were actually negatively charged(electrons). Thus the experiment allowed us to establish that the source of beta decay from Radium-226 were electrons.

-Sundheep

 

Beta Spectroscopy

Beta decay is a radioactive decay involving the emission of a β particle, which may be either an electron or a positron. By the conservation of energy and momentum, all beta particles emitted in any given decay pathway should have the same energy. However, the energy spectrum of beta particles was experimentally determined to be continuous. This is only possible if a third particle, the neutrino () or anti-neutrino (), were also emitted in the decay.

In this experiment, the energy spectrum of beta particles from the radioactive decay of Sodium-22 (Na-22) and Strontium-90 (Sr-90) will be studied. A β particle released in this decay process travels at nearly the speed of light. As such, its relativistic mass, which depends on the motion of the β particle, has to be taken into consideration.

The aim of the experiment was to investigate the energies of the β particles emitted from the radioactive decay of Sodium-22 and Strontium-90, and o verify Einstein’s theory of special relativity of mass-energy equivalence.

X-Ray Physics

When electrons are accelerated using an electric field at high voltages of about 15-35kV, these electrons will attain very high energies.  If an accelerated electron is directed at a metal target and collides with an inner shell electron in the metal, the inner shell electron may be removed and the atom may be ionized if the accelerated electron has sufficient energy to overcome the binding energy of the inner shell electron. This leaves a vacant inner orbital in the atom, making the atom unstable. In order to achieve its stable state, electrons from outer shells fall to occupy the vacant orbital in the inner shell, releasing photons with discrete energies in the x-ray range. Production of x-rays by this process gives rise to characteristic radiation.

In addition to this characteristic radiation, directing high energy electrons at a metal target produces x-rays in a continuous spectrum, due to bremsstrahlung, which means “braking radiation”. This is emitted when electrons travel through the cloud of electrons in the metal without colliding with any of the electrons. The accelerated electrons experiences a strong attractive force as it passes close to a nucleus of an atom, resulting in it slowing down and being deflected. As energy has to be conserved, the kinetic energy lost by the electron in slowing down is converted into radiation and emitted. Photons of produced in this manner may possess any amount of energy and can be detected by the counter if it possesses energy in the x-ray range.

The aim of this experiment is to determine the energy of x-ray quanta with the method of Bragg diffraction.

Hafizah’s reflections (:

My first trip out of Singapore/Malaysia in 10 years, my first flight in 10 years. The trip to Germany was most enjoyable and unforgettable for me and browsing through pictures makes me miss the place even more. This trip has changed my mindset in learning and in science (it’s not all application) and made me realize that passion in the subject makes all the difference.

The moment I stepped out of the airport, the cold breeze hit my face. We had been warned that it would be cold, but I wasn’t expecting such freezing temperatures! (it turned out to be the coldest day of the whole trip) I was so excited to be stepping on a foreign land. As we drove through Frankfurt, I was left awed and amazed by the beautiful scenery and architecture the city had to offer. One thing that struck me the most was the cobbled roads. Where can you find that in Singapore? There’s  just tar and cement. As we walked around in the cold and toured the city, I came to notice the very laid-back lifestyle they had there. It was a stark contrast to the hectic lives of Singaporeans.

Of course, the main purpose of our trip was to delve deeper into the subjects of Physics and Neurophysiology and carry out experiments to better our understanding of concepts. Although we had long days of lessons and experiments day in and day out, there were no complains and in fact, you could see that all of us enjoyed the time spent at Xlab. The learning environment there was very nurturing; the lecturers trusted us with their expensive equipment and allowed us to carry out the experiments independently while going around to clarify any doubts or concerns and explaining in much further detail on the concept that we were testing and its applications. The passion with which the lecturers spoke of their subjects egged you on to find out more about it.

What left the greatest impact on me was the way in which the lecturers analysed the results of the experiments with us. After going through the theory lesson and learning all about the topic and experiment that we were carrying out, we were left to interpret the data on our own and a lot of independent learning was expected of us. When posed with a seemingly unusual result, we had to get our minds working and come up with a logical explanation for it. Spoonfeeding was a no-no. Although we were quite stumped at the beginning, the answer slowly became apparent to us after thinking through it systematically, and the explanation turned out not to be too complicated after all.

From performing the experiments and watching the lecturer’s demonstration, I recognize that experience and skill are really important in experiments. In one particular experiment, we had a hard time trying to carry out the experiment while the lecturer could do it in a matter of minutes. But our determination and focus made up for our lack of skill (and possibly luck) and we managed to complete the experiment in the end.

Besides the academic aspect of the trip, the sightseeing was a great reward for our hard work after a whole day spent in the facility. We visited the town center multiple times (shopping on streets was a great change from Singapore’s many shopping malls), toured the town, saw all the great historical buildings and statues. We even visited the graves of famous scientists such as Heisenberg, Max Planck and Gauss, whom we previously only saw on paper in our lecture notes. On the free Sunday that we had, we got the chance to walk through a mine and see its workings back when it was still active. Walking through fields and up hills for approximately 2 hours, while enjoying the cool air, flora and fauna, just to get to a castle on top of a hill was probably my best memory of the trip. Although it sounds crazy (I’ve never walked so far in my life), all the walking was rewarded with, well, more beautiful scenery but this time at the top of the tower of a medieval castle. Now how cool is that.

Besides just being awed and amazed by just about everything, I learned quite a few things during the trip as well, one of which was awareness of my surroundings. As we were allowed to tour the town on our own, we had to trust our instincts (and our friends’) to navigate our way around and look out for one another and I for one had to be cautious of what I ate, being in a foreign land without the luxury of readily available halal eating places. Punctuality was also of utmost importance as the public bus (our main mode of transport during the trip) ran on a very punctual schedule and arrival times were placed very far apart (due to the small size of the population/town).

My words surely do not do justice in recounting the amazing 11days we spent in Gottingen, Germany. With awesome company in an awesome place, it was a great privilege to be on this trip. This IS the best trip I’ve gone on for a very long time. (:

Reflections – Pan Chuen

This trip was really unique in comparison to the many others the school opens to a large group of people. There were no buddies to bond with, only your school mates for company everyday, and a largely academic focus. It was day in, day out going to the laboratory doing pure science studies, broken only by a Sunday where we had a field trip. Even with this rather bleak description of the trip, I would say that this trip was possibly the best trip that I have gone on with the school, and maybe even the best that I have ever been on.

Don’t get me wrong, the description given is very accurate, but the bleak language was done on purpose. In some people’s eyes, this might be a geek’s paradise come true, to be able to come to XLAB and do all this science. Like many teenagers, I don’t particularly want to be labeled as a geek or nerd, but really, I enjoyed this trip so much that I really think that I am a geek at heart, and so are the rest of the people who went on this trip (haha!), because it was evident that they enjoyed it tremendously as well.

Even though the program only finished at 4-5 pm everyday, being summer, the sun stayed up until past 10. What this meant was that I not only felt a surge in energy late into the night, I was also unable to tell when I should eat dinner. The latter is really a big problem, but the sun allowed us to conduct leisure activities late into the night. I especially appreciate this fact because otherwise, we would not have the chance to explore the beautiful little town called Gottingen to the extent that we did, from the graves of Max Planck, the small shops around town, the university itself, to the house of Otto Von Bismark, the father of Modern Germany. It was great that I had the company of a group of close friends who explored the town together.

The science that we did in XLAB was really memorable, though I hope no one is expecting me to remember all every single minute detail. It ranged from poking locusts with a really tiny pipette (less than 1 micrometer!) in neurophysiology, to playing around with radioactive sources like mad scientists. I have a couple of “mosts” that I took back from XLAB. The most memorable experiment was when we were using the Nd:YAG laser, doing all the diffracting etc. Two things in this experiment really impressed me, the fact that there were invisible lasers, and the fact that these invisible lasers were used to produce green lasers through a frequency doubling crystal. According to the lecturer, this crystal is the reason why green lasers are more expensive. The most visual thing that I remembered was of course, the cloud chamber. Looking at the cloud chamber is somewhat like watching waves, in that it is really calming and relaxing. The different kinds of tracks each kind of radioactive particle makes, to the randomness of everything, make this a vivid image in my mind.

What I cannot even begin to describe in full detail is the culture that I have been exposed to in Germany. The scientists, researchers and lecturers there all share a passion for their subject that I seldom observe anywhere else that I have been. This was particularly evident at the Max Planck Institute of Biophysical Chemistry, when we were given a tour by one of the researchers doing NMR. It was surprising to me how excited he was about his field of study, even though to me, NMR did not seem as interesting and dynamic as some other subjects. Perhaps, it was the desire to be at the forefront of research, basic fundamental research, that drives him to be so passionate about what he does. Humility seemed to be a big part of German culture as well. People from the wives of Nobel Laureates to the common man on the street treated us in the same friendly way, without being overly concerned about where they came from or what they had achieved. Seeing this, I now constantly remind myself to be humble of whatever I have achieved, and to never look down on others who might not be as privileged as myself.

This short trip of 10 odd days has indeed taught me much and will forever stay in my memory. I am deeply grateful to the school and to the teachers who have followed us, themselves being new to the environment and pioneers in the program, for being the steady pillars that they were.

 

Summary – Experiments on the visual system of locusts and humans (Ivan & Pan)

This experiment was split into two segments, one determining the flicker fusion frequency of the human eye, and another regarding the extracellular recording of the DCMD (Descending Contralateral Movement Detector) action potential in a locust.

The flicker fusion frequency is the frequency when individuals flashes of a light source fuses into one continuous flash. This frequency is largely dependent on the agility of the eye in reacting to optical stimulus. In this segment, a computer program controlled the frequency of an LED light source and individuals observed the light source under a microscope to determine whether they could differentiate the different flashes of light. This was done repeatedly until the person just could not observe the individual flashes, which was recorded as the flicker fusion frequency. It was found that the flicker fusion frequency differed from person to person, but was approximately 50 Hz in bright light. Later on, the test was done again with several filters blocking light to different degrees. The reduced intensity of light caused the flicker fusion frequency to drop drastically, suggesting that the brightness of the source also contributes to the flicker fusion frequency.

In the second segment of the experiment, an electrode was placed in the nerve identified as the DCMD of a locust. As its name suggests, this nerve is related to the detection of movement by the visual system of the locust. This segment aimed to record the reaction of the DCMD in the locust to various visual stimuli, varied according to colour and size, in terms of the action potentials generated there. These stimuli were small or large spheres in white, black or grey colours. They were moved towards and away from the locust quickly using a servomechanism.

Normally, the DCMD will have some kind of potential which is basically irrelevant and considered as noise. Thus, a threshold was set on a computer program used to read the potentials recorded by the electrode. The frequency of action potentials in response to a single stimulus was the measure through which we observed the locust’s response. The results showed that only the size of the object caused a significant difference in the frequency of action potentials, with the larger sphere eliciting a higher frequency and vice versa. On the other hand, the response to the other factor was largely uniform, meaning that the locust did not differentiate between the different colours.

A further procedure was carried out, mainly to observe the response of the locust to different frequencies of stimuli. As the time interval between each stimulus is reduced, the response of the locust became weaker (i.e. the frequency of action potentials became lower). This is an adaptation of the locust to frequent stimulus which do not harm itself. Thus, it shows that the frequency of the stimuli could have played a part in the previous result.

Fabia’s Reflections

We spent a total of 8 days at XLAB learning and doing experiments. 4 days were spent on physics and the other 4 on neurophysiology. For neurophysiology, we learnt about cell membrane potentials (measuring the membrane potential of frog Oocytes), ion channels on cell membranes (reading Action Potentials of leech ganglia), weakly electric fish and how they communicate and respond to stimuli and experiments on the visual system of grasshoppers and humans.

The day is usually split into theory and experimental; we spent mornings on the theories and afternoons doing experiments. The experiments really helped to reinforce the knowledge gained from the lecture. There were certain things that cannot be learnt unless done hands on. For example, measuring the membrane potential of Oocytes. It sounds easy to make a tiny glass pipette by just placing it in a machine and filling it with a solution before carefully inserting it into the Oocyte. However, when we got about actually doing it, it got really hard. It really needed patience and skill to aim the pipette carefully into the Oocyte without breaking or tearing it.

The most interesting experiment for Neurophysiology was the experiment on weakly electric fish. Not only did we learn about how the fishes generate weak electric fields, we also observed how they communicated using these electric signals. There was also a small part were a stimulus (electric conductor and non-conductor) was applied and the response of the fish was observed. The interesting this is that the other fish in another tank connected by wires to the first fish responds to the stimulus applied to the first fish.

For physics, although we have learnt about waves before, but the experiments we did were different from the ones we have done before. In school, we did wave experiments using red lasers and diffraction gratings. The experiments we did in XLAB involved microwaves. The advantage of using microwaves for the experiments is that it has a long wavelength, so the experiments are large scale and the properties of waves can be more easily observed. Below is the picture of a huge experimental set-up.

The laser experiments were also different from the ones we usually do in school. The lasers used in XLAB were huge and we can play around with the individual components of the laser; this really helps in understanding how the laser works.

Apart from lectures and experiments, we learnt about the culture. Although Gottingen is a relatively small town, it is famous for its university and institutes. There were buildings all around town that have been there for a long time; the architecture was old but beautifully designed.

When we traveled by public transport or had dinner at a restaurant, it was quite obvious that we were the noisiest group there. Unlike Singapore, the Germans didn’t speak unless necessary on buses and in restaurants. Although we might attribute that to the difference in culture, but I think it just goes to show how Germans are more considerate of others as compared to Singaporeans in general. I find that the Germans are really polite, humble and punctual in general. The buses really stick to their schedule. Even if it arrives early, it will wait at the stop until the time indicated on the schedule before leaving. This is so that people who come to the bus stop on time will get to take the bus.

We also attended an Organ recital as well as a choral concert. Both concerts were held in churches and the sound effect was simply terrific. For the choral concert, when the choir started singing, the sound just reverberated through the church and made it sound even more sacred. The same can be said for the Organ recital. I think it is rare to have Organ recitals in Singapore, so being able to watch one in Germany is really a privilege.

The highlight for the trip for me is actually the visit to the Goslar mines. Although the day we went to visit the mines was one of the hottest days, when we went into the mine, the temperature just plummeted to below 15°C. I found that the staircases we used to get around in the mine were very steep and terrifying to climb. It is unimaginable how the miners managed to get around using not staircases, but ladders. To make things worse, the mines were not installed with electric lamps; the miners had to use one hand to hold onto a lamp with a small flame while using the other hand to stabilize themselves on the ladders. The flame on the lamp was so small that a tiny drop of water could put it out. Once the flame was put out, the miner would be stuck at that spot in darkness until another miner comes along and relights his lamp. The picture below shows how dark it is with just that tiny flame.

The most amazing thing was the water wheel system built in the mines. The opening and tunnels of the mine were small, but there were parts of the mines that are larger and contained water wheels. Apparently, the water wheel had to be built and assembled nicely outside the mine before taking it apart to be carried into the mines. When all the parts were brought into the mine, the wheel had to be reassembled. Added to the fact that these things were done without the modern machinery we have nowadays, it is an awesome feat.

Lastly, I think that we have to be really thankful to Mrs Lay and Dr Tang for working so hard to bring us to places not planned by XLAB. I really enjoyed the visit to a typical German house as well as to the farm nearby. We also visited several graveyards which had gravestones of mathematicians and scientists like Max Planck. It is really lucky that we had Mrs Lay with us. Without her it might have been much more difficult to communicate with the locals who could not speak fluent English. I would also like to add that I feel very privileged to have gone on this OSAP. I have gained much in terms of cultural experience as well as knowledge in Neurophysiology and Physics.

Yihui’s reflections – Part 2

Continuing on our photo safari…

Day 6 – Last day of Physics

Sadly, this was the last day of Physics Luckily the lecturers made it one worth remembering! Johnny became very excited when I broached the topic of quantum entanglement. In that passionate, meandering way of his, he started to talk very rapidly about the EPR paradox, Maria Goeppert, Bell’s inequalities and Quantum Key Distribution! It was an excellent summary of most of the important developments of the 21st century.

In the afternoon, we learnt about the Nd:YAG laser. We saw for ourselves the phenomenon of frequency doubling, where the infrared light of the laser changed to green upon addition of a nonlinear crystal! This was quite magical, and of course I had to research on this after we went back – unfortunately my attempts to understand nonlinear optics were hampered by an inadequate grasp of Maxwell’s equations

Since it was the last day, of course we had to take photos with our lecturers:

All of Group 1 holding various paraphernalia on the Physics floor, with Johnny and Ellen

After lessons, we visited the Bunte Gotter (Colourful Gods) Art exhibition.

Painstakingly restoring the Bunte to the Gotter

Day 7 – First day of Neurophysiology

In the morning, we visited the Max Planck Institute for Biophysical Chemistry.

OMG, Fourier Transform, what art thou doing here?!

NMR machines at the Max Planck Institute

We started on neurophysiology that afternoon. For our first experiment, we had to poke a needle into an oocyte, the largest cell available.

Poking a needle into an oocyte

A photo of our (successful) experiment! The adrenaline rush upon seeing the oscilloscope reading dip suddenly (signifying the entry of the needle) – exhilarating!

Tricia’s Post Trip Reflections

HI FRIENDS

I enjoyed this trip immensely due to many reasons.

Firstly, this trip gave me an insight into scientific research. I particularly cherished this opportunity as my Advanced Research Project is not laboratory based and I had wanted very much to experience research in a laboratory based setting. Although the experiments we performed at XLAB were guided, something not characteristic of research in general, I still found the experience very fulfilling and felt privileged to be able to use advanced equipment and apparatus for our experiments.

In my opinion, among all the experiments we performed, the second neurophysiology experiment was probably the one that was closest to the nature of the field of scientific research. In this experiment, we had to measure the action potentials generated by a leech ganglion after firing electrical impulses into it. Recording a well-defined action potential pattern was difficult and required much patience. Through this, I learnt to be optimistic and to maintain a positive outlook, as frustration would not have done anything to help the situation. Rather, it would have hindered our progress. Unfortunately, my group mate and I did not manage to finish the experiment in time. Although I felt disappointed, I learnt how disappointment and dead-ends were inevitable in research. I learnt how research was not always a bed of roses, but instead included much brainstorming and head-scratching.

This is the leech whose ganglions we viewed under the microscope

What was especially memorable for me during the trip was the visit to the Max Planck Institute for Biophysical Chemistry. I have read about the institute previously in our school’s textbooks and the number of Nobel laureates that it produced. Thus, being able to visit that institute felt almost surreal and I felt very privileged to be able to visit such a renowned research facility. I’m very glad to have been given such a rare opportunity. To me, the icing on top of the cake was the fact that we were able to view the NMR instrument up close and even learn about the different parts that constitute it! I heard that this was not even a privilege granted to students studying in NUS and thus am very grateful for this experience.

This trip has also allowed me to experience life in a country that does not have English as its first language. We had to pick up certain important phrases and learn useful tips like to not pretend to understand the German language when we do not (TEGUT HAHA lol don’t kill me). We also learnt about how humble and punctual the Germans are. This can be seen by how punctual their buses are and how the German Nobel laureates do not refer much to their title respectively. Overall, I believed that the group of us learnt a lot from the positive qualities of the Germans.

In conclusion, I feel very privileged and grateful to be able to participate in the first XLAB Overseas Student Academic Program. I learnt a lot during this program, and the experience was truly memorable. I may not be fully aware of what goes on behind the scenes, but I know that the coordinators from NUS High and XLAB had put much thought into our program and I am very thankful. I would like to thank Dr Tang and Mrs Lay for keeping an eye on all of us and for scouting all the sites before we visited. I would also like to thank Mrs Lay for translating menus and for arranging the visit to the German household and ‘horse farm’. I hope that the memorandum of understanding between NUS High and XLAB will be signed so that our juniors will be able to experience this next year!

 

ohsix power

Yihui’s reflections – Part 1

Extra Gottingam non est vita, si est vita, non est ita
- Outside Göttingen there is no life. Even if it is life, it is not like here.

This saying is inscribed beside the entrance to the Ratskeller, which is where we had our farewell dinner.  It aptly sums up my feelings – that poignant blend of happiness and longing – upon leaving Göttingen.

So I’ll tell my story through pictures.

Day 1- Frankfurt

Much excitement upon seeing the word 'quark' used to describe a pastry - wow, the Germans are that much into Physics? AWESOME!

Bad Homburg with attached tower

Day 2- Start of lessons at XLAB

Our first sight of XLAB

In the afternoon, we had a tour of the town centre. I’d been to Cambridge previously, and both towns had the same rustic, student-centric charm.

I would love to work in a place like that someday – a place where knowledge is prized, cosy enough that I know my neighbours but with enough cultural activity to keep it a-buzzing! Perhaps a quote from the bust of Rowena Ravenclaw (of Harry Potter) is in order here: “Wit beyond measure is man’s greatest treasure”.

The town was as compact as Singapore!

I do not know why there was a random display of pretty things in the middle of the town centre

Day 3- An invigorating walk to Plesse Burg

In the morning, we did X-ray physics. This was waay more interesting than the experiments of the previous day because it was something new! We used a Bragg crystal to diffract X-rays – an interesting application of the otherwise mundane n(lambda) = 2dsin(tetha) formula.

After lessons had ended, it was time for…

I feel that Dr Tang's polo tee goes very well with the yellow poppyfield

Again - nice colours

When we finally arrived at Plesse castle after a long trek, the panoramic views were stunning.

All of us in the courtyard of Burg Plesse!

Day 4 – Chorale concert

In the morning, we did radiation. Unfortunately we had already done this in school, so I was not looking forward to anything radically different, until…

The cloud chamber was one of the coolest things I saw on the trip!

In the evening, we went back to the town centre.

A wurst - at long last! It was lovely, juicy and oily - too bad the bun was a disappointment.

At the chorale concert in St Johannis kirche!

The choir had an outstanding alto whose voice perfectly complemented the soprano’s – so much so that someone like me (possessing an ear whose training has been undone by years of neglect) could appreciate it. Their rendition of ‘Hallelujah’ was quite awe-inspiring, especially when complemented by a clearly-enraptured Desmond simultaneously belting the lyrics into my ear.

Day 5 – Goßlar

And we had a day off, because it was a Sunday! We took this opportunity to visit Goßlar, a UNESCO World Heritage site.

Looking up in wonderment and awe in the Mines of Rammelsberg

Schweineshaxe - the culinary highlight of the trip

Tricia posing with a chain-mail suit!

It was at this point, I think, that my accursed 4GB memory card ran out of space. Damnation!

The photos after this are of lower resolution because they are taken from my albums in Bradford’s FB account… (long story)