Phonon: Understanding Answers to Q9 and Q10

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In summary, phonons are quantum of vibrational energy in a crystal lattice, created when thermal energy is transferred to the lattice. As temperature increases, the number of phonons also increases. They cannot be directly observed, but their effects can be seen through various techniques. Phonons play a crucial role in determining the properties of materials, such as thermal and electrical properties, and can also affect mechanical properties. Understanding phonons is important for predicting and manipulating material behavior.
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http://qm-web.library.qmul.ac.uk/exams/science/physics/2008/PHY108.pdf [Broken]

Questions 9) and 10).

The resources on them are scarce, can't seem to find understandable explanations for it, could anyone give me a hand here?
 
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I can't access the link you posted...
 

1. What is a phonon?

A phonon is a quantum of vibrational energy in a crystal lattice. It is a collective excitation of atoms or molecules in a solid that can be thought of as a particle-like entity.

2. How are phonons created?

Phonons are created when thermal energy is transferred to a crystal lattice, causing the atoms or molecules to vibrate. They can also be created through interactions with other particles or through external forces such as pressure or electric fields.

3. What is the relationship between phonons and temperature?

As temperature increases, the number of phonons in a crystal lattice also increases. This is because higher temperatures provide more energy for the atoms or molecules to vibrate, creating more phonons.

4. Can phonons be observed?

Phonons themselves cannot be directly observed, as they are a theoretical concept. However, their effects can be observed through various techniques such as neutron scattering, Raman spectroscopy, and inelastic X-ray scattering.

5. How do phonons affect the properties of materials?

Phonons play a crucial role in determining the thermal and electrical properties of materials. They also affect mechanical properties such as thermal expansion and elasticity. Understanding phonons is important for predicting and manipulating the behavior of materials.

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