Which of the following occurs as the wavelength of a photon increases?

• A. The speed of the photon increases.
• B. The energy of the photon increases.
• C. The frequency of the photon decreases.
• D. The frequency of the photon increases.

Answer: (C)

Verified step by step guidance

1. Recall the fundamental relationship between the wavelength (\( \lambda \)), frequency (\( \nu \)), and speed (\( c \)) of a photon: \[ c = \lambda \times \nu \] where \( c \) is the speed of light, which is constant in a vacuum (approximately \( 3.00 \times 10^{8} \, \text{m/s} \)).
2. Since the speed of light \( c \) is constant, if the wavelength \( \lambda \) increases, the frequency \( \nu \) must adjust to keep the product \( \lambda \times \nu \) equal to \( c \).
3. Rearrange the equation to solve for frequency: \[ \nu = \frac{c}{\lambda} \] This shows that frequency is inversely proportional to wavelength.
4. Therefore, as the wavelength \( \lambda \) increases, the frequency \( \nu \) decreases.
5. Remember that the energy \( E \) of a photon is related to its frequency by the equation: \[ E = h \nu \] where \( h \) is Planck's constant. So, if frequency decreases, energy also decreases, and the speed of the photon remains constant.