Engaging questions:
- Why do objects have different colours?
- What is the mechanism of the colour creation?
- What is the colour of light emitted by green jelly bear that is highlighted with a flashlight?
- What is the colour of light emitted by a finger that is highlighted with a torch?
- What is the colour of light emitted by green jelly bear that is highlighted with a red laser pointer?
- What is the colour of light emitted by black jelly bear that is highlighted with a flashlight?
Chemicals: Jelly bears of different colours. Instead of the bears, cuvettes filled with the coloured solutions can be used, they may be the solutions of food dyes (recommended for younger children) or for example:
- green solution: FeCl2 at the concentration of 1 mol/dm3
- red solution: HCl at the concentration of 1 mol/dm3 + methyl orange,
- violet solution: KMnO4 , 1 mol/dm3 (or blue solution: CuSO4 , 1 mol/dm3)
Equipment: flashlights, various colours laser pointers.
Caution! Do not stare into pointer beam!
Description of the Activity :
Students:
1. Highlight jelly bears (cuvettes) by a flashlight.
2. Highlight a finger by a torch.
3. Highlight jelly bears (cuvette) by lasers.
4. Highlight a finger with green and red pointer.
Discussion:
- Why finger highlighted with flashlight is red?
- What is the difference in illumination of objects with laser and flashlight?