**Is the momentum of a photon 0?** **the momentum of a photon would be zero** as well as its energy.

**What is the formula of momentum of a photon?** Photons have momentum, given by **p=hλ** p = h λ , where λ is the photon wavelength.

**What is the momentum of a phonon?** Phonons are merely collective excitations in the lattice. Since the time averaged momentum of each atom is 0, the total momentum of a phonon is also .

**Does phonon carry momentum?** All Answers (4) “A phonon of wavector K will interact with particles such as photons, neutrons, and electrons as if it had a momentum ℏK. However, **a phonon does not carry physical momentum**.

## Is the momentum of a photon 0? – Additional Questions

### Why do phonons not carry momentum?

Phonons ‘apparently’ do not carry momentum though it may appear that phonons carry a momentum . But actually the stuff is different. Phonons are basically collective excitations in a lattice. **Since the time averaged momentum of all the atoms is zero, the phonon momentum also turns out to be zero**.

### What is phonon write expression for energy and momentum of a phonon?

Phonons are quantized particles of sound. Similar to photons, the phonon energy is related to the frequency of the sound waves **E = hf** and the phonon momentum is related to the wavelength of the sound waves p = h/λ.

### What is the difference between photon and phonon?

**A photon is a form of energy but the phonon is a mode of oscillation that occurs in lattice structures**. A photon can be considered as a wave and a particle, which are physically observable entities. A phonon is a mode of vibration, which is neither a wave nor a particle.

### What are phonons in physics?

A phonon is **the elementary excitation in the quantum mechanical treatment of vibrations in a crystal lattice** [1] or the quantum unit of a crystal lattice vibration. They are analogous to photons, having energy of ћω as quanta of excitation of the lattice vibration mode of angular frequency ω.

### What is electron crystal momentum?

In solid-state physics crystal momentum or quasimomentum is **a momentum-like vector associated with electrons in a crystal lattice**. It is defined by the associated wave vectors of this lattice, according to.

### How do you find crystal momentum?

The expression for crystal momentum can be used to write this as, **⃗Fext=m∗d⃗vg(⃗k)dt**, where the effective mass is, m∗(⃗k)=ℏ2∇2⃗kE(⃗k).

### What are Brillouin zones in physics?

In mathematics and solid state physics, the first Brillouin zone is **a uniquely defined primitive cell in reciprocal space**. In the same way the Bravais lattice is divided up into Wigner–Seitz cells in the real lattice, the reciprocal lattice is broken up into Brillouin zones.

### Why crystal momentum is conserved?

The reason is that crystal momentum must be conserved. That is much like linear momentum must be preserved for electrons in free space. **Since a photon has negligible crystal momentum, the crystal momentum of the electron cannot change**. That means it must stay on the same vertical line in the reduced zone scheme.

### What is a phonon mode?

A phonon is **a quantized mode of vibration occurring in a rigid crystal lattice**, such as the atomic lattice of a solid.

### What is electron effective mass?

For electrons or electron holes in a solid, the effective mass is usually stated as **a factor multiplying the rest mass of an electron**, m_{e} (9.11 × 10^{−}^{31} kg).

### What is the Debroglie wavelength?

de Broglie wavelength is an important concept while studying quantum mechanics. **The wavelength (λ) that is associated with an object in relation to its momentum and mass** is known as de Broglie wavelength. A particle’s de Broglie wavelength is usually inversely proportional to its force.