A decrease from 90 to 77 kVp results in which of the following changes?

When kilovoltage peak (kVp) decreases, this affects the energy of the X-ray photons produced. A decrease in kVp means that the photons have a lower energy level. The relationship between the energy of the photons and their wavelength is inversely proportional; as energy decreases, the wavelength increases. Therefore, when the kVp is reduced from 90 to 77, the resulting X-ray photons will indeed have a higher wavelength.

Increasing the wavelength typically corresponds to less penetrating power of the X-rays, which affects image quality and the amount of radiation that can penetrate the body. The other options relate to different aspects of X-ray production or imaging and do not align with the direct implication of a decrease in kVp.