# Is the momentum of a photon 0?

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  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, me (9.11 × 1031 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. 