# Vibrating Objects Part 2

Since I have an answer to Vibrating Objects, I am asking a part two about much faster vibration. What about vibrating an object at 1 THz or higher? What methods can be used? How much energy is spent.

• What type of objects? Electrons, atoms, cars? – jinawee May 6 '15 at 11:58
• 1THz vibrations are in the deep infrared. It's the range of frequencies of certain types of molecular movements. How much energy is in a vibration mode depends entirely on the amplitude. With molecules, of course, that energy is quantized. – CuriousOne May 6 '15 at 12:27
• @jinawee macroscopic objects – Jimmy360 May 6 '15 at 12:27
• Ouch, 2 close votes – Jimmy360 May 6 '15 at 22:56
• Please write the question in such a way that it is self-contained and meaningful. – Neuneck May 7 '15 at 11:51

I doubt you can do that. Let's do a back-of-the-envelope calculation.

Suppose we are dealing with harmonic oscillation.

$$v(t)= 2 \pi \nu A \cos (2\pi\nu t)$$

$$v_{max}=2\pi\nu A$$

where $A$ is the maximum displacement.

You want the process to be macroscopic, so we could take $A=1\mathrm{mm}$, pretty small. If $\nu=1\mathrm{THz}$, we get $v_{max}=0.02c$, where $c$ is the speed of light. For a mass of $1\mathrm{g}$, the associated kinetic energy would be similar to the kinetic energy of an Airbus A380 at cruising speed.

Vibrations at 1 THz and over are mostly molecular or macromolecular vibrations. This is the sort of frequency where you get the vibration of individual atoms in molecules or collections of molecules in larger molecular structure.

When dealing with molecular vibrations quantum mechanics needs to be used and classical pictures break down - so a simple picture of an atom vibrating in a molecule as we would imagine a ball on a spring is not correct.

There is no simple answer to your question, but I can make a couple of points

1) Heating any material will make it 'vibrate' more - but they will not be macroscopic vibrations we can observe or feel by touch - or rather if we feel them we will feel heat instead of vibration

2) lasers/spectroscopy can be used to excite vibrations / observe vibrations - this is a big area

( by the way... 3) THz radiation is used in airports for body scanning....)