Have you ever wondered how Radio picks certain frequencies so you can play your favourite channel or why does a glass break down in an orchestra concert? Have you ever felt a bridge vibrating when you walk on it? Why do you think you encounter such situations? The answer lies in the phenomenon of resonance.
Resonance is a phenomenon in which an external force and a vibrating system force another system around it to vibrate with greater amplitude at a specified frequency of operation. The frequency at which the second body starts oscillating or vibrating at higher amplitude is called the resonant frequency of the body.
Let’s see the examples of resonance that occur in our everyday life.
A playground swing is one of the familiar examples of resonance. When we push the swing, it starts moving forward and backwards. If a series of regular pushes are given to the swing, its motion can be built. The person who is pushing the string has to match the timing of the swing. The pusher has to sync with the timing of the swing. This causes the motion of the swing to have increased amplitude so as to reach higher. Once when the swing reaches its natural frequency of oscillation, a gentle push to the swing helps to maintain its amplitude due to resonance. We call this in-sync motion “Resonance.” But, if the push given is irregular, the swing will hardly vibrate, and this out-of-sync motion will never lead to resonance, and the swing will not go higher.
A guitar produces sound entirely by vibration. In an acoustic guitar when you pluck a string, it vibrates and transmits the sound energy into the hollow wooden body of the guitar, making it (and the air inside) resonate and amplifying the sound (making it considerably louder).
Whereas in an electric guitar when the musician strikes the string, it oscillates and the electromagnetic device in the guitar turns this oscillation into an electric signal that is sent to the amplifier. The amplifier sends oscillations on to the speaker. If the frequency of the speakers matches the vibration of the guitar, it results in sound which is called audio feedback.
The pendulum works on the same principle as the swing. If we push the pendulum it will move back and forth. Continuous pushing at the regular time intervals will cause an increase in the motion of the pendulum. If regular pushes are given to the pendulum, its motion can be built enormously.
4. Singer Breaking A Wine Glass
Have you ever watched or heard about shattering of a wine glass in an orchestra? If yes, then this is all due to the phenomenon of resonance. The natural frequency of glass or any other object is determined by its shape and composition. If the singer’s voice hits the resonant frequency of the wine glass, a transfer of energy will occur. However, the full transfer of energy can cause shattering of glass.
A group of soldiers while marching on the bridge are asked to break their steps very often. Their rhythmic marching can set extreme vibrations at the bridge’s natural frequency. If their synchronized footsteps resonate with the natural frequency of the bridge, it can stagger the bridge apart. So, when designing such structures, the engineers ensure that the resonant frequencies of components are different from those of other oscillating components. The biggest example of the same is the Tacoma Bridge Collapse, in which the frequency of the air matched with the frequency of the bridge, leading to its collapse.
6. Music system playing on the high heavy beat
Have you ever noticed the walls and furniture of your home vibrating when you play music on a heavy beat? This is because the natural frequency of the furniture gets resonated with the frequency of the sound of the music, and, hence, causing them to vibrate.
7. Singing in shower
People who are not very good at singing sound much better while singing in the shower because the pure notes emitted are resonated in the shower cubicle. The bathroom is enclosed space and sometimes small; as you sing the sound waves hit the walls more frequently causing the wall to vibrate since the walls are parallel to each other. The reflected sound hit each other, thereby causing the wall to vibrate at your natural frequency and the louder sound is transmitted.
When we turn the knob of the radio to our favourite channel, we are changing the natural frequency of the receiver. The natural frequency of the receiver then matches the transmission frequency of the radio station. When two frequencies match, energy transfer occurs and we listen to the selected channel.
9. Microwave Oven
The food is heated quickly in a microwave because of resonance. The radiations emitted by a microwave oven have a certain wavelength and frequency. And like all other objects, molecules of water and fat also have a resonance frequency. At a certain frequency, the molecules absorb wavelengths and start vibrating, causing cooking and heating up of food.