Suspensions

A suspension is a mixture made when a substance is insoluble, so the substance floats or sinks. There are three possible ways to separate suspensions:

1. decanting
2. filtering
3. centrifuging

In today's lesson, we had to decide which method is the best. Is there actually a "best" method. We used research, an experiment (p29) and a case study (p30) to help with this.

Primary Colours

Today, we learned about the primary colours of light. These are a little different to the primary colours of paint. This is because paint reflects fewer colours when we mix the colours together. This is called colour subtraction. On the other hand, when we mix the primary colours of light, we add the colours, so more light is let through.

Then, we had to do some research and produce a report or poster about one of the following topics:

• How do we see colours?
• How does theatre lighting work?
• How do televisions work?

The Visible Spectrum

Dispersion is the splitting of white light into the visible spectrum - red, orange, yellow, green, blue, indigo and violet.

These colours are called the visible spectrum.

Our group work for today asked us to show a deeper understanding of dispersion:

As the colours of the rainbow can be created using dispersion, maybe we can combine these colours to make white light again:

Lenses

Today, we learned about lenses. Lenses use refraction to change the image size. Lenses are curved and classified as either concave or convex. Convex lenses are used as magnifying glasses, while concave lenses make things smaller. Convex lenses focus light on a point called the focus.

Then, we got to play with some lenses and rayboxes. After that, we had to compare and contrast different lens types:

This work will help us with our online homework which asks us to explain how glasses are used to help people who are long-sighted.

Refraction

Today, we learned about refraction - the "bending" of light when it goes through water, glass or plastic.

We did an experiment and had a difficult question to answer:

Laser Water

Here is an experiment we did in class about lights and water.

It is just a trick, but how does it work...?!

Shadows

Today we started our light topic. We watched this video, then got to make our own shadow puppets.

We were asked a few questions:

1. How do you make the puppets bigger/smaller?
2. How does this work?
3. What do shadows tell us about light rays?
4. How do we use shadows in everyday life? OR How do we stop shadows causing problems in everyday life?