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Equipment

Slinky
AKA: Wave Form Helix

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Fig 1: Original Slinky
Fig 1

Summary

A long metal spring which can be used to demonstrate the properties of waves.

Operation

Long slinky springs (much longer than the 70s toy) are available from lab suppliers for this specific purpose. They can be used in the classroom in a variety of ways as mentioned in the experiments below.

Longitudinal and transverse pulses

Lay out the slinky and attach one end to a lab stool or other fixed object so that you are facing it end-on. Take the other end and quickly move it about half a meter to the right and then back to the centre to create a transverse wave pattern that should travel along the length of the spring. Compressing the spring about half a meter then extending again will create a longitudinal or compression wave.

Motion of an individual turn

Teachers may want to demonstrate the individual movement of a turn of the coil. Marking one or more of the turns with a piece of tape clearly shows this single movement.

Speed of waves

By altering the tension in the spring and amplitude pupils can investigate how this will affect the speed of the wave.

Reflection

Fix one end of the spring tight and move the other end as in experiment one. As long as the friction from the floor is not acting too much upon the spring movement, reflected waves should return along its length.

Superposition

Send a pulse from each end at the same time and look at the resulting effects. Either the wave will cancel out or double depending on the polarity of the movement.

Standing Waves

Pulse the spring at even intervals until the wave pattern becomes stationary.

Safety

 CautionThe contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.