From Refraction

Today we looked at refraction, which is bending of light. This happens because light travels more slowly in glass and water than in air. Some effects of this are a pencil in a glass looks bent and the deep end of a swimming pool looks shallower than it really is.

In order for refraction to work , the light must hit the boundary of glass or water at an angle ( see the photos to illustrate this)

Homework was set today, which was to complete the sheet by wednesday.

sheet

Homework to be completed by wednesday 7th March

Homework

Today we looked at how many elements in the periodic table are radioactive. We discussed some of their uses :

• nuclear power (uranium),
• weapons(plutonium),
• archeology (carbon 14).

We learned that all radioactive elements lose atoms, and that the time it takes for a sample of radioactivity to lose half of its atoms is called its half-life. We learned that this varies from a few microseconds to millions of years.

In the exam there could be a question where you work out the age of a sample based on how many atoms are left, or you could be asked to predict how long a sample will take to completely decay. You might be asked to label or complete a graph. We worked through some examples in class and will look at some more tomorrow.

You were also asked to complete at home by thursday the following sheet

homework

see also http://home.clara.net/darvill/nucrad/hlife.htm

We revised series and parallel circuits and current and voltage today. Students made some simple circuits to compare. We will continue this topic tomorrow and have a look at some SATs questions.

Today and Friday we took a look at diffusion. This happens in liquids and gases ( and sometimes very slowly in solids) and is the NET movement of particles from high to low concentration. Diffusion is important for us to be able to take in oxygen and get rid of carbon dioxide, and for plants to do the opposite.

Tomorrow we will look at a special kind of diffusion called osmosis.