Physics Narrative pages 3-5
Ask pupils to draw a picture of their eye and then an object. Ask them to draw an arrow to show how they see the object.
Show them that light travels in straight lines and we see objects by light reflecting off of objects and into our eyes.
Practical - Teaching Approaches pages 5-6
Explain that the laser beam is just a highly concentrated beam of light. Ask the pupils what will happen when the laser is turned on. Most will say that they will see the beam of light travel from the laser to the board. When you turn the light on, they will see the dot and not the beam. This is because the light is not reflecting off of anything until it gets to the board, where it is reflecting off and into our eyes. Turn the light out again and then use the talc to show the beam of light. Ask again why they can now see the beam. It is because the light is now reflecting off of the talc particles and into their eyes. It is also travelling in a straight line, which shows that light travels in a straight line.
Seeing with light: teaching and learning issues
Also use the discussion at the end of the practical to generate discussion and to iron out any misconceptions - what happens when a light is switched on? How fast does light travel? Etc etc