Sunday, October 11, 2015

cathode ray oscilloscope by Shamineswari 5 B 2014

I had put up Shamineswari lesson on frog vle last year but I didn't transfer it to physics is fun blog.
Shamineswari 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.

I am thinking how do I load a whole power point up on a blog post?
i shall try to put the link and see if it works.

Oh oh the link didnt seem to work.

I think if you copy and paste the link - you should get her beautiful powerpoint as i have uploaded it on Google drive.

Have fun trying

Thursday, May 2, 2013

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.

Sunday, March 31, 2013

Hot Air Balloons fiesta in Putrajaya

Life is simply very good because God orchestrates everything,
including hot air balloons on Easter.

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!

Sunday, April 15, 2012

Rekha's powerpoint on gradient

Rehkha from 5 Bakawali 2012 has done this presentation on steps involved in calculating the gradient of a slope. Thsi question always comes out in Paper 3 ( 3 marks) and in Peka . It  also occasionally in Paper 1 and 2.

I am trying to upload Rekha powerpoint - I hope it succeeds.

There is always room to learn through trying out something new.

Congrats Rekha for doing a great pience of work.


Pn Tan

Wednesday, November 30, 2011

God leaks Physics questions? He does?

I happened to drive into school from the district education office in Sentul almost immediately after the Physics SPM Paper 2 2011 ended. I waved at my students streaming of the school gate and met some girls lingering at the car porch!

Boy,  they were excited! They told me with glee - "Teacher - Resonance came out! We all can remember so well teacher did the experiment at the assembly !" Then Sabrinah and Kayathry said - "Yes teacher - we did the peer teaching lesson for resonance and it came out! Yeah!!"

The girls had done this very funny lesson on resonance where
everybody in the class laughed after they saw the video of the
opera singer breaking the glass by her soprano voice.

I enjoyed getting very feminine slides from Sabrinah and Kayathry.
After all this is CONVENT Sentul! Feminine slides
are simply so refreshing after all the co-ed schools
and the co-ed slides

So I asked the girls whether they remember when they did the resonance peer teach project. They said - "In March." I said " Wow, God has been loving you gals and leaking the SPM question to you since March and you didn't know and weren't even conscious He was loving you by making you do the very project that would come out in SPM !"

Then I recieved lovely emails from the girls who had left earlier and who didn;t get to talk to me after the paper.

It was for the resonance lesson I borrowed the guitar from SMK Seksyen 5 Lab! It was well worth asking my ex- lab assistant to send the guitar all the way to SMK Convent Sentul! And I did the resonance expeiment at assembly and spoke my Principal's motivation speech from it on teamwork and one frequency and one spirit. No wonder the girls remember the lesson so well!

The actual SPM question and my girls loved it!

Then in Paper 3, another question was " leaked" by God right from my first lesson with 5 Anggerik. Read the email and see if you understand why Dorothea was so happy!

So - you see God does leak exam questions even with us being aware of it at all and He leaks it way beforehand - right from my first lesson and first experiment with my students. I feel so good knowing this , that right from the very start God's presence and love  was in our classroom leading us to vital truths in Physics and in life without us having a clue. Haha!

Wednesday, August 31, 2011


Almost a year ago, last Hari Merdeka in 2010, I decided to celebrate Merdeka by starting a blog on Physics. Exactly one year later, I am still going on strong and I now maintain several blogs. I am glad I decided to celebrate Merdeka last year by doing this little something different - blogging! The prime mover for the Physics blog was because my ex-headmistress, Pn Habshah came to Seksyen 5 in July 2010 and asked all Panitia to start writing a panitia blog. Thank you Pn Habshah!

Actually the opportunities for learning Physics via the Internet is literally limitless! Usually there are some topics your teacher haven't quite finished teaching or some topics you don't quite understand.  I do know many of you are quite worried as all the Physics topics will be tested on in the Trial SPM 2011.  I also know many schools have not quite finished the syllabus, so how do you begin to learn on your own?

Simple!  Just google whatever topic you need to learn for example, CRO movies or electronics movies or radioactivity movies - especially the last 3 topics which you haven't quite finished and you will find many many videos of teachers teaching these topics or funny videos showing you how to understand the lesson.

The following are the links on electronics

The major difference between learning on the net and live from your teacher is that when you have questions, you can ask your teacher and in real life you have a relationship where your teacher and you enjoy one another's friendship and development.

Also your teacher can give you short cuts and tips to learning. For example, I like to use the Happy Family concept when teaching logic gates.  Secondly I introduce the logic gates by using an automatic artificial intelligence based on the binary system which only have two numbers 1 and 0 as in the case of the automatic piano in my music box.

This music box plays music automatically without
a human musician because of the binary system. Do you see the baby piano
in the music box?When the piano keys meet the white dots, they are raised and the input is 1.
When the keys meet the grey section the keys are down =0.
This means by positioning the white dots, I can raise the piano keys
and play a tune according to how I program the position of the white dots.

The AND gate is a very strict family when the father or Ayah (input A) and the mother or iBu (input B) have to agree ( be 1) before the Child gets ( output C) gets to go out and have fun any where ( output 1). The Boolean logic is simply A.B which means A multiply by B ie 1 x1 = 1 but 1x 0 = 0.
My short cut tip is the symbol looks like D for darab and D dor DAN which is BM for AND and multiply

In the OR gate, the family is less strict so if either father or mother says yes, ( input on 1) the child gets to go out. The OR gate already looks less strict since the lines are curved which means means the parents are not so straight laced or strict. The Boolean logic is A+B so if daddy A says yes = 1 but mummy says no = 0, the child gets to go out because 1+0 =1

In the Not gate, there is only 1 input so it is a bit like a single parent fanily with a rebellious child so if the parent input says yes,(1)  the defiant child says the opposite (0). My apologies to single parent families for using this allegory bcause not all children of single parent family are that rebellious.

Then you have the NAND ( Not + AND) which is really a very very rebellious child ie both parents says yes but the child says no. Similarly the NOR gate.

The exclusive gate is a little tricky. The parents are on the verge of a separation so if daddy appears, mummy won't appear and the party can be held without quarrels and vice versa but if both daddy and mummy appear, they will quarrel and the party is a no no.

You can see from the the 2nd row of the truth table for the X Or gate that if daddy A does not come (0) and mummy B comes (1) , then the child will have a party (1) but if both daddy and mummy comes as in the last  row, there will be a BIG quarrel and no party (0)

So I am trying to teach on line what I could not cover in the class. See how much you can understand and remember and come meet me on Friday in 5 M if you have questions.

Cheers and don't get so stressed out by Physics!

Tuesday, July 19, 2011