Thinking Allowed

The distance between repeating parts of the pattern (the length of each single wave) is known as the wavelength (l).  Wavelengths can be measured from anywhere to the next identical part of the wave.

Frequency is a measure of how often something happens in one second. The symbol of frequency is f and the units are hertz (Hz). The relationship between velocity, frequency and wavelength is:

 Velocity (m/s) = frequency (Hz) x wavelength (m)

Light waves travel much faster than sound waves. The speed of a set of waves can be found by using information about the distance travelled and time taken or from information about the frequency and wavelength.

Distance, speed and time are connected by:

Speed (m/s)   =   Distance (m) / time (s)

Example An echo takes 1.5 s to reflect from the front wall of a school building 250m away. What is the speed of sound in air?

Distance for echo = 2 x 250 m = 500 m                                Time taken   = 1.5 s

Speed = distance/time = 500/1.5 = 333m/s

This method is practical at school only for the measurement of the speed of sound.

Example Capital Radio broadcasts throughout the London area using radio waves of frequency 1548kHz, travelling at 300000km/s. To what wavelength would you tune a radio to receive Capital programmes?

Speed   = 300000km/s = 300000000m/s                  Frequency = 1548 kHz (1 548 000 Hz)

Wavelength = speed/frequency  = 300 000 000/1 548 000 = 194 m 

Using your knowledge of the wave equation, and the relationship between frequency and time [f = 1/T], answer the following questions:-

1. If the waves in the ocean are timed so that they come to shore every 1.74 seconds, what is the frequency of these waves? (Show your working and don’t forget units).
2. A radio wave has a frequency of 2 MHz (2 MegaHertz = 2 000 000 Hz). Calculate the time period between successive waves.
3. A radio station broadcasts with a wavelength of 160m. If the velocity of the radio signal is 3 x 10⁸ m/s, calculate the frequency of the wave. 
4. If all the 1.2 billion people in China jump up and down at the same time, they will create a shock wave that will travel around the Earth in all directions.  This wave will focus and peak on the other side of the Earth, exactly opposite China (around California).  If the circumference of the Earth is 40 000km and the speed of sound on the Earth’s surface is 2850m/s, calculate how long it will take for California to crumble into the sea due to the shock wave.

Grade 9 Integrated Science 1 docwaves practice questions mark scheme

green sine by bdu on flickr

New topic – yay!  We’ll learn about waves.  Here are some of the points we’ll try and answer:-

• What is a wave?
• What is the difference between transverse and longitudinal waves?
• What are some examples of transverse and longitudinal waves?
• What are the amplitude, frequency and wavelength of a wave?

Anatomy of Waves

We’ll then take a look at the wave equation       v = f λ

This shows us the relationship between speed of a wave v, the time it takes for a particle to vibrate up and down, and the distance between successive waves λ.  You’ll need your calculators as we practice solving problems in class.

ghosts of semesters passed by foreverdigital on flickr

Here are the syllabus guides for the core (SL) and HL topics for the entire IB Bio course.  The syllabus guides for the options we have studied are in previous posts.

For SL – you need TOPICS 1, 2, 3, 4, 5 and 6 only.

For HL – you need all the above PLUS TOPICS 7, 8, 9, 10 and 11.

Topic 1 – Statistical Analysis 2009 Syllabus   Topic 2 – syllabus outline  Topic 3,7,8 – syllabus outline   Topic 4 – Syllabus outline  Topic 5 – syllabus guide  Topic 6 – syllabus outline  Topic 9 – Syllabus outline  IB Biology HL Topic 10 – syllabus guide  Topic 11 – syllabus guide

Before you know it, mocks will be over, then Easter break, then in a few short weeks it will be May and you’ll start the REAL IB exams… and then graduation and tears of joy and sadness and a new chapter will begin…. One step at a time.  Keep studying.  It will end.

Check out lottolab.  Watch the TED video and then play around the site.  There are loads of optical illusions to keep you entertained.

And now get back to your mock revision….Friday 19th March is looming!

peacock by vigilant20 on flickr

Here’s what we need to cover in this last section of Option E.

1. Honey bees are social organisms.  Describe the organization of a bee colony – who does what.  Find one other example of such social organization and describe it. #1 2 Social Organisms
2. What is the role of natural selection in colonies like this?
3. Give 2 non-human examples of altruistic behaviour and discuss in terms of evolution.  Altruistic Behavior in animals
4. What is foraging?  Bluegill fish forage for Daphnia.  Find one other example, and explain how this type of behaviour optimizes food intake. E6 notes #3 4
5. Peacocks have pretty fancy tail feathers.  Why have they evolved this way? Explain in terms of mate selection. #5 animal behavior   Peacocks #5
6. Animals show rhythmical variations in activity.  Outline 2 examples illustrating this.  Eg, seasonal reproductive behaviour in deer. Rythmical Variations

Here’s a very useful slideshare presentation on this section.

fMRI by nats on flickr

This next section, E5, is all about the human brain, brain function, fMRI, sympathetic and parasympathetic nervous systems, pupil reflex, brain death, and the perception of pain.  Phew!  That’s a lot of concepts. 

We’ll again use click4biology as a good resource, and this presentation from Mr Taylor in Bandung to help us get through it all.  Here are the key questions we need to answer:

• What are the major parts of the human brain, and what are their functions?
• How do animal experiments, lesions and fMRI scanning used in identifying which part of the brain is involved with specific functions?
• How are heart rate, movements of the iris, and blood flow to the gut controlled by the sympathetic and parasympathetic nervous systems?
• What is the pupil reflex and how is it used to determine brain death?
• How is pain perceived and how to endorphins help to alleviate it?

This is also a very useful set of notes, courtesy of Mr Hobbins. Topic E5 The Brain

Coal transport by MoToMo on flickr

For our culminating activity in this unit we will be getting you into groups and asking you to research, present and debate on which is the best source of energy for the Philippines.  Look at this handout for full details of the work, including the rubric for assessment.  Amended Energy Topic Performance Task

Each group of 4 students will be given one source of energy.  Each person on the group will take on a different role – either that of engineer, economist, environmentalist, or a  member of the public – and put together a convincing argument as to why their particular source of energy should be used.  You will also need to have some knowledge of other sources of energy in order to be able to counter any arguments against your source. 

Solar Panels by clownfish on flickr

You will be given 2 full lessons to research this.  The next lesson we will listen to each presentation, make some notes on this sheet: ENERGY PERFORMANCE TASK Presentation Notes and then vote on which energy source we think should be used.

This should be fun!

Current world oil reserves by ChartsBin on flickr

In class today we discussed the idea of exponential growth and watched this video by Chris Martenson.  We discussed the idea of peak oil, and how this was different to “oil running out” by watching this video.  We then researched which countries have oil reserves, and how much, and discovered that according to CIA world factbook, that the Philippines is #62 on the list.

We will discuss the following essential questions:

• Why have humans become so much more productive over the last 250 years when compared to the previous 250,000?
• What is peak oil, and should we be worried that some people say we have reached it?
• What will be the consequence of an ever increasing human population and falling fossil fuel energy reserves?
• Will developing countries ever realize the standard of living enjoyed by people in developed countries?

Sharkwater by thegreenpages on flickr

After watching SHARKWATER in class, where we discussed many of the issues surrounding food webs and man’s impact on them, particularly in the ocean, I found this article in the news today, so thought I’d share it with you.

Imagine you are a carbon atom in a molecule of carbon dioxide in the air.  Close your eyes.  Really imagine yourself as that carbon atom.  Your task is to describe the journey you take from being part of carbon dioxide in the air, through the carbon cycle, until you return to the air again.  Here is my attempt at the beginnings of such a story to give you the idea.  You do not need to start in this way.  You decide.  Get creative!  Let your imagination work!

There I was, happily floating around in my usual gaseous form along with several of my brothers and sisters  (other carbon dioxide molecules), and my good friends nitrogen and oxygen.  We were having a great time bumping into one another, when I got dangerously close to a leaf.  Everyone had always told me to stay away from green plants, that I could get sucked into a stoma and never be seen again.  Before I realized what was happening, I was inside a chloroplast and going through a very fast reaction where I had to let go of my two oxygen atoms, and for a moment be entirely alone.  Before long, I found some other carbons and we joined together, 6 of us, 12 hydrogen friends and 6 oxygen buddies to form a glucose molecule….