Question

Does a photon emitted by a higher-wattage red light bulb have more energy than a photon emitted by a lower-wattage red bulb

Answer 1

Answer:

The energy of these two photons would be the same as long as their frequencies are the same (same color, assuming that the two bulbs emit at only one wavelength.)

Explanation:

The energy $E$ of a photon is proportional to its frequency $f$. The constant of proportionality is Planck's Constant, $h$. This proportionality is known as the Planck-Einstein Relation.

$E = h\, f$.

The color of a beam of visible light depends on the frequency of the light. Assume that the two bulbs in this question each emits light of only one frequency (rather than a mix of light of different frequencies and colors.) Let $f_{1}$ and $f_{2}$ denote the frequency of the light from each bulb.

If the color of the red light from the two bulbs is the same, those two bulbs must emit light at the same frequency: $f_{1} = f_{2}$.

Thus, by the Planck-Einstein Relation, the energy of a photon from each bulb would also be the same:

$h\, f_{1} = h\, f_{2}$.

Note that among these two bulbs, the brighter one appears brighter soley because it emits more photons per unit area in unit time. While the energy of each photon stays the same, the bulb releases more energy by emitting more of these photons.