5. What is the basis of vibrational spectroscopy. Derive the expression for natural frequency for vibration of a spring with spring constant K and mass m.

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**Question 5:**

*What is the basis of vibrational spectroscopy? Derive the expression for natural frequency for vibration of a spring with spring constant \(K\) and mass \(m\).*

### Explanation:

Vibrational spectroscopy involves studying the vibrational states of molecules. The molecules absorb energy at specific frequencies, leading to molecular vibrations observable through techniques like infrared and Raman spectroscopy.

### Derivation:

To find the natural frequency (\(\omega\)) of a spring-mass system:
- The system follows Hooke’s law and Newton’s second law.
- The force on the mass is given by \( F = -Kx \), where \( x \) is the displacement.
- From Newton’s second law, \( F = ma \), where \( a = \frac{d^2x}{dt^2} \).

Equating the two expressions for force:
\[ m \frac{d^2x}{dt^2} = -Kx \]

This differential equation can be rearranged as:
\[ \frac{d^2x}{dt^2} + \frac{K}{m}x = 0 \]

The solution to this equation is harmonic motion:
\[ x(t) = A \cos(\omega t + \phi) \]

Where: 
- \( A \) is the amplitude,
- \( \phi \) is the phase,
- \( \omega \) is the angular frequency and is given by:
\[ \omega = \sqrt{\frac{K}{m}} \]

Thus, the natural frequency (\(f\)) is:
\[ f = \frac{\omega}{2\pi} = \frac{1}{2\pi} \sqrt{\frac{K}{m}} \]

This formula expresses the natural frequency of vibration for a spring system with stiffness \(K\) and mass \(m\).
Transcribed Image Text:**Question 5:** *What is the basis of vibrational spectroscopy? Derive the expression for natural frequency for vibration of a spring with spring constant \(K\) and mass \(m\).* ### Explanation: Vibrational spectroscopy involves studying the vibrational states of molecules. The molecules absorb energy at specific frequencies, leading to molecular vibrations observable through techniques like infrared and Raman spectroscopy. ### Derivation: To find the natural frequency (\(\omega\)) of a spring-mass system: - The system follows Hooke’s law and Newton’s second law. - The force on the mass is given by \( F = -Kx \), where \( x \) is the displacement. - From Newton’s second law, \( F = ma \), where \( a = \frac{d^2x}{dt^2} \). Equating the two expressions for force: \[ m \frac{d^2x}{dt^2} = -Kx \] This differential equation can be rearranged as: \[ \frac{d^2x}{dt^2} + \frac{K}{m}x = 0 \] The solution to this equation is harmonic motion: \[ x(t) = A \cos(\omega t + \phi) \] Where: - \( A \) is the amplitude, - \( \phi \) is the phase, - \( \omega \) is the angular frequency and is given by: \[ \omega = \sqrt{\frac{K}{m}} \] Thus, the natural frequency (\(f\)) is: \[ f = \frac{\omega}{2\pi} = \frac{1}{2\pi} \sqrt{\frac{K}{m}} \] This formula expresses the natural frequency of vibration for a spring system with stiffness \(K\) and mass \(m\).
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