Constructive Interference
Light, Sound and Waves

Laser Slinky

Enrichment Activity for 5-11 11-14

What you need

  • A metal slinky
  • Disposable cup
  • Sticky tape
  • Scissors


  1. Turn the cup upside down so that the base is facing you.
  2. Carefully use scissors to make a small hole. Ask friend to help.
  3. Insert about 3 cm of the slinky through the hole in the cup, stick it in place using sticky tape.
  4. Hold the cup and let the slinky drop. Tap the bottom of the slinky and it’ll make laser noises!

Results and Explanation

Slinkies make sound because they vibrate when they stretch out. When they vibrate, they make the air around them vibrate. Both the cup and the air inside it vibrate with the vibrations of the slinky. These build up, and the sound gets louder. This is called amplification.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.

Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today