22.1 Energy and Momentum of a Photon

Photons

What is a Photon?

A photon is a quantum of electromagnetic radiation

Photon Energy

The energy of a photon having a frequency $f$ is given by:

$$E=hf$$

Where $h$ is Planck’s Constant ($6.63\times 10^{-34}{\text{ m}}^2\text{kg}{\text{ s}}^{-1}$)

Photon Energy using Frequency

$E=hf$

Photon Energy using Wavelength

$E=\frac{hc}{\lambda }$

Insight

More energetic photons have a higher frequency and a lower wavelength (Recall that $c=f\lambda$)

The Electronvolt ($\text{eV}$)

Recall

$\text{Voltage}=\frac{\text{Work Done}}{\text{Charge}}$ $\text{Work Done}=\text{Voltage}\times \text{Charge}$

Math

For an electron