Which of the following correctly describes the relationship used to calculate the energy of a photon?

• A. E = h u
• B. E = h / u
• C. E = c / u
• D. E = m c^2

Answer: (A)

Verified step by step guidance

1. Recall that the energy of a photon is related to its frequency by Planck's equation, which connects energy (E) and frequency (\( \nu \)).
2. The correct formula is given by \( E = h \nu \), where \( h \) is Planck's constant and \( \nu \) (nu) is the frequency of the photon.
3. Understand that \( E = h / \nu \) is incorrect because energy is directly proportional to frequency, not inversely proportional.
4. Note that \( E = c / \nu \) is incorrect because \( c \) is the speed of light and does not directly relate energy to frequency in this way.
5. Also, \( E = m c^2 \) is Einstein's mass-energy equivalence formula, which is not used to calculate the energy of a photon based on frequency.