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Lovely light beam

You will need:

  • A clear plastic bottle and water nearby
  • A flashlight
  • Sticky tape
  • Aluminium foil
  • A dark room



1. Wrap the sides of the bottle in aluminium foil.

2. Fill the bottle with water and turn off the lights.

3. As you turn the bottle upside down to pour the water out, shine the torch through the base of the bottle.

4. The light shines through the water and creates a beam of light that pours from the mouth of the bottle.
lovely light beam pouring out of a water bottle

What is going on?

The light is internally bouncing within the water stream. producing a nicely focused beam of light.
Light travels through optical cables in a similar fashion, bouncing through the cables to convey information between users.

This process of light bouncing within a substance as it travels is known as Total Internal Reflection.
Find out more about this process here.

Try using a laser pointer with adult supervision... does this work better than the flashlight? Why?

Be Amazing Book Front Cover; Ben Newsome, teacher & founder of Fizzics Education. Be Amazing -how to teach science the way primary kids love
Be Amazing!
How to teach science, the way primary kids love

Read more about Be Amazing
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