Friday, 3 June 2011

EXPERIMENTS ~ #2 - Sound Waves & How They Travel

Can you see the "ring-shaped" waves??
Ian F. Mahaney also gave directions for a second experiment in his book "Sound Waves."  On Page 22 he tells readers, " Sound travels in waves.  These sound waves travel through the air in all directions.  Here's a way to show how sound waves work."

To do this experiment we needed:

sink, tub or plastic dishpan filled with water
food colouring

Here are the instructions:

"STEP 1 - Fill a sink, tub, or plastic dishpan with water.  Add a few drops of food colouring.  Drop a pebble into the water.  What do you see?  Ring-shaped waves travel out in all directions.

STEP 2 - Try dropping two pebbles in the water at the same time but in different places.  Two pebbles make two sets of waves that pass through each other.  Sound waves move like this.  That's why you can hear several different kinds of sound at one time."

When we were doing this experiment, Alisdair and I first chose a small stainless steel bowl and filled it with coloured water.  When we dropped a pebble in it, we couldn't see anything significant.  Then we decided that perhaps we did not have enough water and should do the experiment in the kitchen sink.  It worked!  However we had to be very coordinated to get these photographs -- Alisdair would drop the rock on the count of three and I would quickly snap the camera!

Alisdair says:  "This was a much quieter experiment.  We recommend it if you don't want your ears ringing!!  If you look very closely at our pictures, you can actually see the rings in the green water.  I got to choose the colour of food colouring.  In the book they used blue, but I wanted to use Saskatchewan Roughrider green!  (Sorry Winnipeg Bluebomber fans!)  It was fun to be allowed to drop stones in the water just to see the rings they made.  Now I know why they put ripples in comic books when something falls into a pool of water or when there is an echo.  It was an easy experiment but I am glad we did it."   

You can see the waves in the water and the rock in this photo.

The patterns when we dropped two rocks into the sink.
The brown flecks in the photo are weird.
  I think they are a reflection from the light above the sink.
The publisher of this book, "PowerKids Press" has an online list of websites, for additional exploration, which is updated regularly. Two of these sites are on the topic of sound waves.

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