# Is the momentum of a photon constant?

Table of Contents

- 1 Is the momentum of a photon constant?
- 2 Does a photon have energy and momentum?
- 3 What is the momentum of a moving photon?
- 4 What is the energy of a photon of light?
- 5 Does photon have energy?
- 6 Do photons have energy?
- 7 Can light energy push objects?
- 8 What happens to energy and momentum when photons collide with electrons?
- 9 What is photon momentum and how does it work?
- 10 Why can’t massless photons have momentum?

## Is the momentum of a photon constant?

The momentum of a photon is instead related to its wavelength and can be calculated using the formula 𝑝 = ℎ 𝜆 , where 𝑝 is the momentum of the photon and ℎ is the Planck constant, as before. Notice that the momentum of a photon is inversely proportional to its wavelength.

## Does a photon have energy and momentum?

Yes it does. Although the photon has zero rest mass, it does have energy. From the relativistic relationships among Energy, Mass, and Momentum, E2 = (Moc2)2 + (pc)2, if the rest mass is zero then the momentum is give by p = E/c.

**How much energy must a photon have if it is to have the momentum of a 10 Mev proton?**

The total energy of the 10MeV proton would be 948.28MeV because the proton rest energy is 938.28MeV.

### What is the momentum of a moving photon?

The momentum of a photon, p, measured in kilogram meters per second, is equal to Planck’s constant, h, divided by the de Broglie wavelength of the light, lambda, measured in meters (p = h / lambda).

### What is the energy of a photon of light?

The energy of a single photon is: hν or = (h/2π)ω where h is Planck’s constant: 6.626 x 10-34 Joule-sec. One photon of visible light contains about 10-19 Joules (not much!) the number of photons per second in a beam.

**Can photons push matter?**

The crucial point is that while light doesn’t accelerate, and doesn’t have mass, it does carry momentum and momentum, as a form of energy, can be transferred. By transferring their momentum, photons are able to exert a force on an object. This means that blue light will push you stronger than red light.

## Does photon have energy?

Since photons (particles of light) have no mass, they must obey E = pc and therefore get all of their energy from their momentum. If a particle has no mass (m = 0) and is at rest (p = 0), then the total energy is zero (E = 0).

## Do photons have energy?

Light is composed of photons, which have no mass, so therefore light has no mass and can’t weigh anything. Not so fast. Because photons have energy — and, as Einstein taught us, energy is equal to the mass of a body, multiplied by the speed of light squared.

**What is the energy of each photon?**

### Can light energy push objects?

Light carries momentum that can push on an object, but it can also move an object through thermal forces. Light can also exert force through the photophoretic effect, where preferential absorption of light on one side of an object leads to a temperature difference that causes the object to move.

### What happens to energy and momentum when photons collide with electrons?

Some of the energy and momentum is transferred to the electron (this is known as the Compton effect), but both energy and momentum are conserved in this elastic collision. After the collision the photon has energy hf/and the electron has acquired a kinetic energy K. Conservation of energy: hf = hf/+ K

**How did Compton see the effects of photon momentum?**

Compton saw the effects of photon momentum because he was observing x rays, which have a small wavelength and a relatively large momentum, interacting with the lightest of particles, the electron. Example 1. Electron and Photon Momentum Compared

## What is photon momentum and how does it work?

In fact, photon momentum is suggested by the photoelectric effect, where photons knock electrons out of a substance. (Figure) shows macroscopic evidence of photon momentum. The tails of the Hale-Bopp comet point away from the Sun, evidence that light has momentum. Dust emanating from the body of the comet forms this tail.

## Why can’t massless photons have momentum?

This is given as a solution to the problem of only massive objects being affected by gravity. However, momentum is the product of mass and velocity, so, by this definition, massless photons cannot have momentum.