# When we talk about natural frequency of an object in the context of resonance, what exactly is vibrating, the electrons or the entire atoms?

And how exactly do objects acquire "natural frequencies"? Is it due to the temperature and the lattice structure (the type of bonds they form with other atoms)? And thus, is resonance just a phenomenon that preserves energy within the lattice than leak it outside?

And is the below illustration accurate for explaining resonance?

Case 1: A hollow metal sphere. Say its natural frequency is 20 Hz. So, if we hit it with a hammer and the resultant energy (by accident/chance) makes it vibrate at 20 Hz, then it takes $$n$$ seconds to cool down and loses $$x$$ Joules to the atmosphere as heat energy (per second).

Case 2: Same sphere as above. We hit it with another hammer but more forcibly. It vibrates at 22 Hz in the beginning, and because that's not its natural frequency, it comes to a standstill at $$n+4$$ seconds, losing $$x+4$$ Joules as heat energy in the process (per second).

Case 3: Same sphere as above. We hit it with a smaller hammer, lightly. It initially vibrates at 18 Hz. Since that's also not the right frequency as the natural one, it loses energy fast but not as fast as Case 1, as the total energy, in this case, is also low (Law of Equilibrium says that one side has too much energy, it loses energy fast to reach the equilibrium). Say it takes $$n+2$$ seconds and loses $$x+2$$ energy per second.

What if we increase the impact in Case 1 by a thousand times (assuming the object doesn't break)? Will the resonant frequency still last longer than the frequency generated by the impact? Is there a threshold that tells the exact amount of energy that is required to cross this resonant threshold of losing energy?

• IMO, if you want to understand "natural frequencies" (a.k.a., "resonance") you should start by learning what makes a pendulum work and then, by learning the equations that govern a simple harmonic oscillator. Got to understand the basics before you move on to more complex systems like your ringing metal sphere. Aug 4, 2021 at 12:32
• Why use a sphere, when you can use a mass on an ideal spring? Also, the resonance cases are unrelated to the title...is this 2 different questions?
– JEB
Aug 4, 2021 at 14:18
• When you whack your sphere, it's motion will be complex--a superposition of multiple, three dimensional vibration modes. When you are ready to understand the math behind that, then you will be ready to dive in to quantum mechanics. No Joke! It's literally almost the same thing. That's why you should start with something simpler. JEB is right: a mass on a spring is better than a pendulum. But note: you'll be working with differential equations--It was 12th grade math when I was a kid, but I don't know what schools teach today. Aug 4, 2021 at 15:22