A decrease in photon energy results in which of the following?

When photon energy decreases, the frequency of the photon also decreases, and the wavelength increases. This relationship is grounded in the principles of electromagnetic radiation, particularly the equations that link energy, frequency, and wavelength.

The energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength. The equation E = hf describes that the energy (E) is the product of Planck’s constant (h) and the frequency (f). When the energy is reduced, it follows that the frequency also must decrease because they are directly related.

Simultaneously, wavelength (λ) and frequency are inversely related through the equation c = fλ, where c is the speed of light. If the frequency decreases, the wavelength must increase in order to maintain the constant speed of light. Thus, when photon energy decreases, one observes a decrease in frequency along with a corresponding increase in wavelength, confirming that the answer is correct.