# Questions tagged [vibrations]

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### The definitions of coherent phonons and acoustic phonons

I found that the definition of coherent phonon: A femtosecond laser pulse can initiate collective, in-phase atomic motions in solids called coherent phonons. My question is: what is the difference ...
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### Can someone please explain how is the setup stated below apparently causing amplitude resonance in spite of different frequencies?

Suppose I have a pendulum such that its natural frequency is $2 Hz$. I release it from One extreme by striking it with a tuning fork of frequency $1 Hz$. Now in $0.5s$, the pendulum will undergo 1 ...
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### Are Harmonic or Subharmonic resonance the only outcomes for a system with applied vibrations?

I'm working on performing a linear stability analysis on a system with fluid undergoing applied vibrations. Now, usually these systems are analyzed with no fluid velocity. Under these conditions, it ...
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### Birefringince in 2D array of masses and springs

Assume a 2D square array of masses with mass $m$ connected by springs with constant $\kappa$. Then the equation of motion for small perturbations in the plane of the array to the mass at $(l,n)$ is  ...
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### Vibrational spectroscopy energy spectrum

I have a question regarding vibrational spectroscopy. In vibrational spectroscopy we are describing the vibration of molecules with the Morse potential which gives us stationary wavefunctions that ...
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### Why is an ultrasonic transducer able to send energy into a tank without an opposing surface?

The diagram shows an ultrasonic transducer stuck to the bottom of an ultrasonic cleaning tank full of water/detergent. It's not supported at the opposing end - just hanging off the bottom of the tank. ...
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### Source term and potential term in wave equation

I have often seen the wave equation as: $\Box \psi(x_1,x_2,x_3) + V(x_1,x_2,x_3)\psi(x_1,x_2,x_3) = S$; where $V$ represents the potential term ans $S$ represents the source term. I want to know that ...
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### How do you Determine the Fastest Vibrational Mode of a Crystal?

I understand that a crystal's vibrational modes are Phonons and have a minimum wavelength that is limited by twice the equilibrium separation between neighbouring atoms. But I don't understand how you ...
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