Photon energy

The energy of a photon is usually found with the formula which uses Planck’s contant:

E = h\times f

Where:

Remember, this finds the energy of a single photon. If you have a beam of light, you would need to multiply this by the number of photons in the beam to find the total energy.

Finding from wavelength

We know that we can find the frequency using f=\frac v\lambda, from our topic on wave speed. Since the speed of light is constant, c, we can use that to find the energy of a photon from its wavelength:

E=h\times \frac{c}{\lambda}=h\times\frac{3.00 \times 10^8}{\lambda}

Where:

flashcards

QuestionAnswer
What is the formula for finding the energy of a single photon using Planck’s constant?E = h \times f
Where E is energy in joules, h is Planck’s constant (6.63 \times 10^{-34} J·s), and f is frequency in hertz.
How do you find the total energy of a beam of light?Multiply the energy of a single photon by the number of photons in the beam.
What formula gives photon energy from wavelength?E = h \times \frac{c}{\lambda}
Where c = 3.00 \times 10^8 m/s and \lambda is wavelength in meters.
What is the value of Planck’s constant, h?Approximately 6.63 \times 10^{-34} joule-seconds.
What is the speed of light, c, used in photon energy calculations?Approximately 3.00 \times 10^8 meters per second.
What is the unit of energy for a photon?Joules.
What is the unit of frequency for a photon?Hertz.
Which equation relates frequency and wavelength for light?f = \frac{c}{\lambda}