The video above shows the amazing gravity-defying optical illusion that won the 2010 Best Illusion of the Year Contest earlier this week.
Using optical illusions in science lessons never fails to amaze students. This particular one could be used as an engaging starter to any lesson on forces.
For a more ‘hands-on’ approach, a gadget that can be bought quite cheaply and shown to students is the hologram chamber. The video below shows this in action. When I have shown it to students in the past they have been completely fascinated and it makes a great basis for a lesson on ray diagrams and forming images.
Showing the students the hologram chamber or the video would be a good starter; students can then give their initial thoughts on how it works before showing them the inside.
This PowerPoint can then be used. It contains two slides. The first is a student sheet that can be printed out and given to the students. They can draw rays on the diagram in order to explain how the gadget works. This gives them an application of using the law of reflection. The second slide shows a completed diagram and an explanation as to how it works, which can be displayed to the class.
This reminds me of a thinking exercise which can be used as a follow-up to this. Imagine a completely sealed room whose walls and ceiling are all mirrors. There is a single light bulb on the ceiling lighting the room. Eventually the light bulb blows. Does the room stay lit up forever?