The energy of a photon with frequency $f$ is given by which of the following expressions, where $h$ is Planck constant?

Solution

1. The energy $E$ of a photon is related to its frequency $f$ by the Planck-Einstein relation.
2. This relationship states that energy is the product of the Planck constant $h$ and the frequency $f$.
3. The resulting formula is $E=hf$.
4. Hence the answer is (B).