Resonance
Driving a system at its natural frequency produces large oscillations.
About this topic
Resonance occurs when a system is driven at its natural frequency, causing large-amplitude oscillations as energy builds up efficiently. Pushing a swing in time with its motion is the classic example.
It makes musical instruments loud, lets radios tune into stations and MRI scanners work. It can also be destructive: soldiers marching in step have damaged bridges, and the Tacoma Narrows Bridge collapsed in 1940 due to wind-driven vibrations. Engineers add damping, which absorbs energy, and detune structures to avoid dangerous frequencies in earthquake zones and in car bodies.
Worked example: a wine glass has a natural frequency near 500 Hz. A singer who holds that pitch loudly makes the glass vibrate with growing amplitude until it may shatter. A child on a swing of period 2 s needs a push every 2 seconds, a driving frequency of 0.5 Hz, to build up a big swing with tiny pushes.
The sharpness of the response depends on damping: light damping gives a tall narrow peak, heavy damping a low broad one. A misconception is that resonance needs a large force; very small repeated pushes at the right timing can build large motion. Another is thinking resonance only occurs with sound; it happens in electric circuits, atoms and buildings too.
Key ideas
- Swings and glasses resonate
- Bridges can fail
- Tuning radios use resonance
Quick check
Use cases: where Resonance helps
- Homework: review the key idea behind Resonance before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Resonance without notes.
- Visual learning: play with the interactive lab to see how Resonance changes when you adjust its inputs.
- Teaching a friend: explain Resonance in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Resonance?
Driving a system at its natural frequency produces large oscillations.
What will I learn in Resonance?
Swings and glasses resonate. Bridges can fail. Tuning radios use resonance.
Is Resonance part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Resonance lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Resonance?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.