Parabolic Reflectors from the time period before Christ till the future

We often see telecomunication systems with huge parabolic satelit discs and antennae. How did Man discovered their usefulness? When did it start? I like to begin with a simple question. How did Roman emperors communicate with their many citizens back in the good old days before the invention of the PA systems or electricity? Well the answer lies in the unique buildings they built. You may be familiar with one particular such famous building in Rome. It is the Colisuem. And it has a unique shape which is termed parabola. I usually teach via an activity. Look at the picture of Year 10 students carrying out an activity with wine glass during our online class

This unique shape is excellent for transmitting sound if the emperor was at the focal point. To demonstrate this, students or teachers carry out the wine glass experiment. The wine glass is filled with water and a finger is pressed on the rim whilst moving it around. A loud sound will be produced due to the unique parabolic shape of the wine glass. I made a short video for you so you can watch and produce the sound. I will put the video links and picture links in the Google classroom that I have set up. Learning has to be experiential. What process are involved to produce the sound? The main process is reflection of sound from the parabolic reflector.This was what the Roman emperors used to communicate with their many citizens. When travelling overseas, I make a point to visit amphithertres and enjoy the miraculous effect of sound transmission.

This is one of me in Athens in Greece.The biggest amphithertre I have been in is the ancient one in Ephesus in present day Turkey. It seats 26,000 people and it still work. During the pandemic, I could not travel to East Malaysia to teach due to the lockdown. I used Zoom and Google Meet to teach the teachers of SK Methodist Kapit the parabola lesson. I was most happy when the teachers sent me videos of thir students having learnt how to do this activity. Now that I have learned and am using Google Classroom, I can see immense potential to teach more online classes and I am quite excited

While we can hear the sound, we cannot see the sound waves so this process of reflection is best demonstrated by using a parabolic mirror and light rays from the Hodson Light Box Kit

Fun with Padlet

Padlet offers immense scope for teaching and learning. It is a fun bulletin board. I am still figuring it out and playing around with it. Here the link to a padlet I made.

Mathematical Calculations

In my slot with Help University, I wanted to cover some basic simple steps of Mathematical calculations but I didn't manage to in view of time constraints. So I will cover them here so that Physics students can systematically use these simple steps.

When reading a mathematical problem, shortlist information given which can be in the form of words or from the diagram. Then focus on the task or assignment or what you are supposed to calculate. Then select the appropriate formula from the list of formulae given in the 2nd page of the exam script. Subsequently substitute in the values and calculate the answer in the unit.

I shall begin with simple calculations and eventually proceed to more difficult ones. I have used different colours coding to show the different steps for example short list information is written in brown, the task is in green, the formula selected is purple with the 1st mark given beside it, the 2nd step of substitution in pink with the 2nd mark and the final mark is in blue for correct answer and unit. Sometimes the formula mark is omitted but the steps should be followed as the examiner can given marks for correct substitution and final answers with ecf ( error carried forward). This means the student can get some marks for the steps even if the final answer is wrong. In Physics, the focus is on the right steps and not just the right answer.

Our second example is as below.

Our 3rd example has slightly higher diffculty level.

The 4th example. I will no longer use the color coding but the steps are the same.

The 5th example

The 6th example

For the 6th example, Hooke's Law is used but this is the spring being compressed rather than being extended. The 7th example shows the calculation of resistance in parallel and is then added to show the total resistance. The voltmeter reading is proportional to the ratio of resistance which is 4 ohms in the total of 6 ohms. The last reading is the total voltage divided by the total resistance.

Do try to be calm when calculating - if you follow the steps, you will get some marks for the method. All the best for SPM!

Of nuclear reactors and relearning true perspective

It's been quite some time since I last posted on the Physics is fun blog but the passion and love for Physics stays. Recently during my trip to the States, we were on the ferry to Kelleys Island - one of the many islands on Lake Erie in Ohio.

In front of Kelleys Island school

We cycled all around Kelleys Island.

During the ferry ride on Lake Erie to Kelleys Island 

Lake  Erie  is  one  of  the 5 great lakes in North America and my geography teacher Mrs Ong made sure I could draw the map of North America free hand and place and name the 5 great lakes. Using the pneumonic HOMES, we name the lakes as Huron, Ontario, Michigan, Erie and Superior.

Can you see the distant nuclear reactor and cooling plant?

Whilst on the ferry ride and while cycling around the  island,    Frank pointed out the nuclear reactor   with   its  cooling plant  nearby  the  lake  to  me.  It  make sense to build the nuclear reactor  close  to  the  lake. The cold glacial waters   would   greatly  helped  to  cool  down  the cooling plant. The reactor looks very small  but I tried to make it clearer by using the red box to highlight it.

The reactor and the cooling plant looks
clearer in this enlarged picture.

What  I  was  amazed  was  that  the  dimensions  of  the nuclear reactor was much smaller compared  to  the size of the cooling plant. Either that or the cooling plant is way nearer to Lake Erie to  make  the  cooling  process  more  efficient.  I  also  noted  there was a sizable distance between the reactor and the cooling plant as seen from the  above  picture. These 2 realizations posed a dilemma to my mind.

For years I had successfully taught my Science and Physics students to draw the fairly complicated labelled diagram of the nuclear reactor and cooling plant as below.

They would first draw the egg shaped reactor  and the vertical fuel and control rods spaced in between. Then they would draw the horizontal graphite in the core and showed how the heat flowed out at the top as hot gas to the heat exchanger or cooling plant. The cold water  would come in at the bottom as  from the cold glacial waters of Lake Erie. Horrors! Now only do I realize I had taught it wrongly for so many years by blindly following the textbook diagrams.

My aha moment in learning and teaching  the reactor came from the dimensions of size and distance! The textbook picture I had taught my students to draw for years were not accurate in dimensions with a wrong perspective on size and distance. In reality, the reactor egg is way smaller as perceived from my photo in contrast to the textbook diagram which made the reactor look bigger than reality. Another truth that shocked me was the reactor was actually situated pretty far away from the cooling plant and not next to each other as I was led to wrongly believe from the textbook diagram.

So travel and first hand experience teaches better perspective and feeds a better grasp of reality compared to textbook diagrams. So maybe the textbook need to label the reactor  diagram as not to scale and put a footnote to indicate the reactor is way smaller than the cooling plant and the distance between them can be several kilometers away. We also need to learn, unlearn and relearn as part of our journey in education and life.

I also had the good fortune to visit Thomas Alva Edison's birthplace and birth home in Milan, Ohio, courtesy Frank's decision to detour to Milan before heading home to Lodi.

Thomas A Edison was born in Milan, Ohio near Lake Erie in 1847.

Thomas Edison's house was very near (about 700 feet )  to  the  Milan Canal.  The Canal  saw big schooners  and  international  sailors  come  inland  via the rivers and Lake Erie. Edison's innovative  spirit  could  have been sparked off by the daily exposure to brave sailors from all over the world who  were  willing  to  risk  their  lives  to  fulfill  heir dreams of travelling and seeing the world, even though if it was by schooners.

Behind Thomas Edison's house.

The map showed international sailors reached
Milan daily via the Milan canal.

The Milan Canal closed up after the invention of the
locomotive made land travel more viable than sea travel.

Edison's early childhood exposure to these brave  sailors daily could have shaped his thinking to be radical rather than conventional. This attitude probably was one reason behind his many inventions. Edison held the record with 2332 patents for inventions for many years. His record was only recently surpassed  in 2003 by Yamazaki. So students and teachers, don't always look  to textbooks as the gospel truth. Travel and actual experience can be better teachers. Exercise your brain via HOTS and really think rather than memorize. Learn to  adjust your perspective on sizes and distances and priorities in life.

Learn, unlearn and relearn when you need to. Learn the real truth and do not be afraid to change the way you think and hopefully then we may become as creative as Edison.

Cathode ray oscilloscope CRO by Shamineswari 5 B 2014

I had put up Shamineswari from SMK Convent Sentul cathode ray tube lesson on frog vle last year but I didn't transfer it to this blogsite physics is fun blog. I also found some very good videos demonstrated and recorded by my ex-students of SMK Sekysen 5 Wangsa Maju on the CRO. I like this video done by Nazrin. https://www.youtube.com/watch?v=UNW8pXbSKv0

I also recorded the Maltese cross shadow deflection video in the link below https://www.youtube.com/watch?v=NoPd5dP9QF4 In view that the SPM new syllabus has new content focussing on photoelectric effect, I thought it good to add the links to these videos here. Back to Shamineswari, she had a very challenging time in 2014 particularly in May when she had dengue and also other medical complications and she could not take her mid year paper.

I remember visiting her in Sentosa Hospital and she and her mum were really surprised to see me at her bedside.

Fyi, fast forward to March 2022, Shamineswari had graduated as a dentist from Faculty of Dentistry, University of Malaya. She received the Dr Solmi Abdullah Award for Outstanding Female Graduate

Interference fringes

I was in Kota Kinabalu last week for a week long conference of 785 school principals from all over Malaysia. The highlight of the conference for me was the talk by Datuk Wira Ameer Mydin ( the Mydin shops CEO) and a most wonderful bench marking visit to SM La Salle, Kota Kinabalu.

 I was fortunate my hotel room had a window view of the sea and I watched several beautiful  sunsets through my window.

The view while being beautiful reminded me of a SPM exam question.
"What is the colour of the sky above you at sunset? 
What is the colour of the sky in front of you at sunset? 
Why do the colours of the sky differ at different positions and at different times. 
Give your explanation with the help of labelled diagrams.

Then when sunset was almost over, I drew my lace curtains and caught this view.

I wonder if this picture causes you to think of anything in Physics. Can you see wavy bright and dark lines in the sections where the curtain folds and pleats are? What do you think these wavy lines are?

They are actually interference fringes, the bright lines being constructive interference and the dark lines being the destructive interference. For interference to occur,there must be 2 coherent sources. These two coherent sources are in the top fold of the curtain and the bottom fold of the curtains. Notice you only see the light fringes where the two different curtains pleats or folds are located - one big fold near the center and one smaller fold near the side.

I remember the first time I visited Pulau Redang almost 23 years ago in 1990. During that trip, there were 2 Physics teachers among many English teachers. Suddenly we two Physics teachers saw the interference fringes on the seabed!! The white sandy sea bed was a perfect screen for interference fringes to show up. Notice the wavy fringes below the sea turtle. I wonder if you can identify the very bright points and very dark points of constructive interference and  the semi bright dark lines of destructive interference.

Suddenly there,  we two Physics teachers realized the ripple tank experiments are actually simulations of the water waves at the sea. We got so excited and jumped up and down in the sea and laughed for joy in the hot sun with the English teachers thinking we two had gone crazy.  You see, it was only then  we realized the lamp at 50 cm height above the ripple tank represent the distant sun which give parallel rays. The waves on the sea are represented by the waves we create in the ripple tank. The white screen is inspired by the white seabed.

Recently while I was in Putrajaya for the hot air balloon fiesta, I bought the giant Stinson Soap Bubble Kit and we played giant soap bubbles both in the Form 5 and Form 3 motivational slot in school. I first saw these giant soap bubbles in San Francisco . Children are always fascinated by soap bubbles whether they be big or small and in this pic, you see children running to play with the soap bubble. But do you see the colorful wavy interference fringes in the soap bubble? Interference occur because the two coherent sources are the top of the soap film and the bottom of the soap film in the bubble.

Just like the curtains, the two coherent sources are very near to each other.  This is why the distance between the two slits in the Young double slits are so close. We had fun doing the Young double slit experiment with the green laser and red laser lamps ( RMB 30/- ) I bought from Shanghai but sorry we forgot to take photos. Next time ....!

Enjoy Physics - it add beauty and wonder to life.

Hot Air Balloons fiesta in SMK Padang Tembak 2002 and in Putrajaya 2013

My students in SMK Padang Tembak had built and launched many different types of hot air balloons to understand Archimedes' principle.

When we first began, many of our hot air balloons launches failed but we learnt much from the failures. Gradually our hot air balloons rose higher. The yellow cellophane balloon launched at 12 noon ( note the short shadows) rose a little -about 5 feet above their heads.

The white mahjong paper hot air balloon launched at 10.30 am rose to about 10 feet above their heads. Our best balloons were the red cellphane balloons which they launched at about 8.00 am. This one rose swiftly above the school's highest block of 4 storeys and we released the pull back string to that balloon and it rose until until it became a little speck in the sky.

To me and my students teams, their balloon launches were fun, meaningful and memorable because they had learnt with their whole being, i.e. pyschomotor, cognitively and in the affective realm. My other tagline for learning is Hands-On, Heads-On, and Hearts-On Learning in that order. I always believe first in teaching via pyschomotor skills - through our hands, our feet as that will stimulate our thinking - our brains and finally when we see the impact of learning upon ourselves and others, the joy of learning comes in.

We spent two nights in our Cyberjaya Summerglades homes for the 5th Malaysian Hot Air Balloons fiesta on 29-31st March 2013. Since our houses were not quite furnished yet, we stayed in Andrew Seoh's house and had 7 stars service right up to the last minute of our stay. Thanks Andrew and Lydia! We never quite fully expected  what would happen in this short stay!

We woke up early to catch the hot air balloons launch in Putrajaya. Listening to the birds chirping at dawn just outside our house is just so therapeutic. We were also blessed to catch sunrise over the Putrajaya Lake just outside Summerglades.

In physics, it is necessary for the balloons to be launched early in the morning so that the  cool temperature in the morning outside the balloon is much lower compared to the hotter temperature inside the hot air  balloon. Can you see the flames heating up the air in the red Tune Talk hot air balloon? The flames make the density of the hot air inside the balloon  much lower than the density of the cold air outside the balloon in the early morning

Another thing to realize is the size of the balloon compared to the actual basket. Can you see how big the volume V of the balloon must be. If you look very closely, you can see near to my head, the small wicker basket with the captain inside it,

 Buoyant force must exceed weight for the balloon to take off.  The buoyant force can be increased by increasing the volume V and ensuring the density of the cold air outside the balloon is higher. Weight can be reduced by making the density of the air inside the balloon to be lower by heating it up. Hot air rises because it is less dense.

The best treat for me and Joanne, Lydia and Andrew was watching the balloons descend. We did not know it beforehand but the balloons had targeted to descend on the grounds near Tun Dr. Mahathir house just next to my house in Summerglades. I heard the sound of hissing gases and saw the balloons coming over Summerglades. I quickly retrieved the keys to my house. I  found Joanne also awake. Both of us watched balloons descend from my back balcony. Then we clambered over the window onto my front balcony and had a first class seat to the balloons landing. Wow! I can see again God is  the Master Conductor who orchestrated events in perfect timing and location to give zest and pleasure to His children.

Joanne strikes a classic pose on my balcony
with the Holland hot air balloon flying past us.
Lydia struck a conversation with the captain on
her balcony  while the balloon flew past Lydia.

We ran excitedly to see how and where the Holland balloon would land. We discovered it just outside the grounds of Summerglades.

We watched the captain clambered outside the wicker basket which held at least 3 big  gas tanks. She instructed her partner to quickly detach the strings from the wicker basket. Another guy ran about 100 m and to pull the main string of the balloon very strongly. This would enable the balloon to land safely on one side. About 9 men or more were involved in this tricky procedure of landing and deflating the balloon.

The  Dutch partner jumps up the wicker basket and
detach the strings. The Malaysian crew catches the string
 with the flag and hold it tight and moves it away from the balloon.

This guy ran like lightning to catch the string to
bring down the balloon.

The grey lines are the fencing in between us within Summerglades
and the  balloon outside. It takes many men to deflate the balloon

One great moment was when Captain Munic from Holland, came by and said hello to us. Joanne and Captain are all smiles as they posed for this photo with Summerglades grey fencing in between them. Captain Munic says she observed rules and did not land inside the housing areas. Joanne is smiling because we have so many unexpected happy bonuses this beautiful Easter morning.

Another bonus. We also had the pleasure to view the motorised paragliders fly around Putrajaya and over Summerglades.

One more bonus. When we returned to Andrew's house, we found he had gone out and bought roti canai telur for our breakfast. And he had viewed so many balloons landing over Summerglades in the course of buying us breakfast.God rewards you, Andrew.

When we finished our breakfast, we drove like lightning back to KL to offer praise and worship to God in TOD at Easter. Christ rose this Easter morning many years ago! Today the risen Christ has caused all our spirits and hopes to rise again as we see how He orchestrated the hot air balloons for us.  Praise God a zilliion times!