A little girl is swinging in a park. His father pushes the swing now and then.The Swing has one frequency of oscillation.The father's frequency of pushes should match that of the Swing.Than only the swing will oscillate well. Here, the phenomenon "resonance" comes into play. We will see one more example.
An opera Singer Sings in high pitch. At one point of time, a wine glass Kept on a table breaks into pieces. Here, the frequency of the Singer matches the natural frequency of the wine glass. Hence, the glass vibrates violently and breaks away. Again resonance.
In 2000, on the London millennium bridge, Some 2000 people walked on it. It caused heavy wobbling of the bridge . The Engineers shut down the bridge immediately and made Some structural modifications to dampen resonance.
So what exactly is resonance? Let us study the definition.
" phenomenon of increased amplitude that occurs when the frequency of a periodically applied force is equal or close to a natural frequency of the system on which it acts."
we will see more interesting facts and the processes of Resonance.
1.SEASHELL
If you hold a sea shell or thermos flask close to your ear . You can hear Some booming sounds. Even a Silent room has Some ambient noise in a range of frequencies. One of those frequencies matches the natural frequency of the shell or flask and resonance occurs. we get an amplified Sound.
2.MUSICAL INSTRUMENTS
First Some basis: Frequency of vibration of an instrument mainly depends on its length. In a flute, trumpet; the vibrating air column determines the frequency.The length of the air Column can be adjusted by opening and closing the holes or by sliding the pipes. In stringed instruments like guitar, the length of the metal String decides the frequency.
Mostly Standing waves take place in musical instruments. A Sound wave travels through the air Column or metal string and reflects back . Both the waves(same frequency) interfere constructively, stand and oscillate. That is, crest and crest of the waves meet; trough and trough meet; they reinforce each other;produce big amplitude waves and well defined music. Once again, Resonance is the basis of musical instruments.
3.Microwave oven
Standing waves also occur in the microwave oven. The generated microwaves reflect back and forth in the cavity of the oven and produce standing waves. These stationary waves agitate water molecules in the foods . Consequently the food is heated up. Here also, waves interfere constructively and produce high amplitude waves. Again, Resonance in action.
4. High-rise buildings
High-rise Buildings may be disturbed or damaged by strong earthquakes . The buildings can be protected by using resonance principle. In the top floor of the building, a 'device' called ‘Tuned mass damper’ is installed. It is Something like a pendulum. A heavy mass like 660 tonnes is attached to the TMD. When the building Oscillates due to an earthquake, the TMD oscillates in the opposite direction; Hence, it dampens and arrests the vibration of the building quickly. Here, the frequency of TMD matches that of the building. But, they oscillate out of phase and get destroyed mutually. In Japan, the high-rise tower by name Taipei -101 was once attacked by an earthquake of magnitude 9.0, the tower was saved by TMD. The video clip is available on the web. The Engineers use this principle to protect Standing rockets, mobile towers, ships, bridges etc.
5. LASER
Let us take the example of a ruby laser or red laser . In the ruby material, a ruby molecule is excited to emit a red pulse of light. This pulse of light induces further emissions. All the emitted light waves have Same frequency and Same phase. Hence, the resonance phenomenon takes place. A High amplitude, powerful, energetic pencil of light is given out. The light beam is So energetic that you can even cut metal with it. By the way, LASER stands for " Lightwave amplification by stimulated emission of radiation". Here, Amplification takes place because of resonance.
6. LCR circuit
A capacitor (pair of plates), an inductor (coil of wire)and the Resistors are all connected by wires. The capacitor is charged up a battery and then the battery is removed from the Circuit. Now, electrical Oscillations are Setup in the Circuit . That is, an alternating current (AC) flows through the circuit. The frequency of AC is decided by the values of capacitor and inductor. This frequency is called the natural frequency of the LCR circuit.
Next, we will connect an AC voltage Source to the Circuit and we will Send alternating Current of various frequencies into the LCR circuit. Only for a particular frequency, the Current will be maximum in the Circuit. This happens when AC frequency matches the natural frequency of LCR Circuit. Hence this circuit is also called resonant circuit. This Circuit has many applications in Electronics.
Let us draw a graph between frequency and Current for this Circuit . The plot is given here. This is the universal Curve of Resonance. That is, maximum occurs when the frequencies match- at a particular frequency.
7. Magnetic resonance imaging-MRI
Our body is mainly made up of water. The water molecule has one Oxygen atom and two Hydrogen atoms. The Hydrogen Atom is nothing but Single proton. The positively charged proton spins with Certain frequencies. Using an MRI machine, we Send radiations of matching frequencies into the body. The protons absorb these radiations; flip up; flip down, and emit back the radiations. The radiation is received, analyzed and an MRI picture is produced by the Software. (Note, we have not gone into details of the MRI technique). MRI is an important diagnostic tool in medicine.
8. Resonance in atom
We Know, electrons revolve in the orbits in all the atoms. We also know, an electron behaves like a wave.The electron cannot revolve in any orbit. It can revolve only in a particular orbit where the wavelength of electrons exactly fits in. That is, the Circumference of the orbit must be a whole number multiples of wavelength. Then, standing waves will occur and constructive interference will take place( see the illustration). As the electron revolves, crest and crest will meet also trough and trough will meet; resonance occurs. Hence, the electrons can move in these orbits without destroying themselves. These orbits are called non-radiating orbits. The resonance is required even for the Survival of the atom.
9. Resonance in mathematics
consider the following formula. Sin(2*pi*f*t)+i COS(2*pi*f*t) . It is a complex number . It also describes two sine waves in perpendicular directions. f is the frequency and t is the time. Let us plot this complex function. If both the frequencies match, we will get a perfect circle. If not, we will get other irregular shapes. Actually, this is the famous euler's formula.
Moral of the Story:
Without resonance, this universe cannot function.The married couple should have resonance in Some traits, then only they will grow and shine. So, tune in with your life partner.
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