Marvin and Milo
Explore physics the exciting way, by trying out a simple and fun experiment. This month, "Doppler Spin". Don't forget to check back next month for the next edition...
Doppler Spin
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What you need
A buzzing egg timer
A piece of string ~1 m
Sticky tape
A friend
Instructions
- Tie the piece of string to the egg timer securely, using some sticky tape as well if needed.
- With the timer buzzing, hold the other end of the string very tightly and start to swing it in a circle around your head. Make sure your friend is standing well back and there’s nothing breakable near you.
Results & explanation
Your friend will hear the pitch of the egg timer change as it moves around your head - but you won’t hear any change at all!
As the egg timer circles towards your friend, the sound waves bunch up closer together and the pitch of the sound gets higher. As it circles away, the sound waves spread out and the pitch becomes lower. Your position relative to the egg timer is always the same so you don’t hear any difference.
Find related websites on the Doppler effect with physics.org
