Photon energy and power

Now we know how to find the energy of a single photon, we can find things involving the power of a beam, or the number of photons in a beam in a given time.

Calculating the number of photons from energy of a single photon

if we are told:

• The power of the beam (in watts)
• The energy of a single photon (in joules)

Then we can find the number of photons emitted per second with the formula:

n = \frac PE

Where:

• n is the number of photons emitted per second
• P is the power of the beam (in watts)
• E is the energy of a single photon (in joules)

Calculating the power of a beam from the number of photons emitted per second

If we are told:

• The number of photons emitted per second
• The energy of a single photon (in joules)

Then we can find the power of the beam with the formula:

P = n \times E

Where:

• P is the power of the beam (in watts)
• n is the number of photons emitted per second
• E is the energy of a single photon (in joules)