# Photon Momentum and Effective Mass | Summary and Q&A

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August 20, 2022
by
The Organic Chemistry Tutor
Photon Momentum and Effective Mass

## TL;DR

The video explains how to calculate the momentum of a photon using Planck's constant and the wavelength of the photon.

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### Q: How can the momentum of a photon be calculated?

The momentum of a photon can be calculated by dividing Planck's constant by the wavelength of the photon. This formula is derived from the equation for the energy and rest mass of the photon.

### Q: What is the significance of a photon having no rest mass?

The fact that a photon has no rest mass means that its energy is solely dependent on its momentum, and changing the wavelength of a photon will cause a change in its momentum.

### Q: How does changing the wavelength of a photon affect its momentum?

Changing the wavelength of a photon directly affects its momentum. Decreasing the wavelength increases the momentum, while increasing the wavelength decreases the momentum.

### Q: What is the effective mass of a photon?

The effective mass of a photon, which is treated as mass in the momentum equation, is determined by dividing Planck's constant by the wavelength of the photon and multiplying it by the speed of light.

## Summary & Key Takeaways

• The momentum of a photon can be calculated using Planck's constant divided by the wavelength of the photon.

• The derivation of the formula for calculating the momentum involves the energy and rest mass of the photon.

• Changing the wavelength of a photon causes the momentum to change as well.