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

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

Answer: (D)

Verified step by step guidance

1. Recall the fundamental relationship between the speed of light (\(c\)), wavelength (\(\lambda\)), and frequency (\(\nu\)) of a photon: \[c = \lambda \times \nu\] where \(c\) is a constant (\$3.00 \times 10^8$ m/s).
2. Since the speed of light \(c\) is constant, if the wavelength \(\lambda\) increases, the frequency \(\nu\) must decrease to keep the product \(\lambda \times \nu\) equal to \(c\).
3. Next, consider the energy (\(E\)) of a photon, which is related to its frequency by the equation: \[E = h \times \nu\] where \(h\) is Planck's constant (\$6.626 \times 10^{-34}$ J·s).
4. Because energy \(E\) depends directly on frequency \(\nu\), if the frequency decreases (due to an increase in wavelength), the energy of the photon also decreases.
5. Finally, the speed of a photon in a vacuum is always constant (\(c\)), so it does not increase or decrease with changes in wavelength or frequency.