Page 19 - FOUNDATIONS FOR LIFE; EXPLORING GOD’S UNIVERSE
P. 19
THE SPEED OF SOUND
Truth to Teach (Source)
It takes time for sound to travel
Sound reflections and echoes
Sounds travel at different speeds through different materials
How bats hear
Way to Work (Means)
Equipment: Stop-watch, string, spoons
1. Review the previous lessons.
2. Show a picture or a video/DVD of a thunderstorm and talk about why we hear the thunder after
the lightning.
Light travels at 186,000 miles per second or 750 mph
Sound travels at 300,000 km per second or 330 mph.
3. Show pictures of bats and find out how much the children know about how bats hear. (They make
a squeaking noise and use their sensitive ears to pick up echoes from surrounding objects.) This is
called echo-location. They can fly in the dark and find food using this method.
Ships use echoes to detect fish, wrecks and submarines. Sound waves are sent down to the sea
bed from an echo-sounder. Time taken for the echoes to bounce back can be used to work out the
position and shape of objects underwater.
Talk about the way in which we hear echoes when sound waves hit a barrier like a cliff so the
waves bounce back and we hear them again. This is evident in a cave.
4. Experiment: Tie two spoons in the middle of a length of string and jingle them together. Now
press the ends of the string into your ears and jingle the spoons again. How is the sound
different? (The sound is louder and deeper the second time because the sounds are passing
through the bones in your skull.)
5. Give the children chance to try this experiment for themselves. Some children may like to find out
more about bats or echo-sounders on the Internet.
6. Notes and labelled diagrams could be written up at the end of the lesson.
Learning for Life (Fulfilment)
The children will have gained more factual knowledge about sound but also recognise the amazing way in
which God has created some creatures to survive, e.g. bats. He has also given man the ability to invent
such instruments as the echo-sounder.
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