What effect does cosmological redshift have on light?

Cosmological redshift primarily refers to the phenomenon where light from distant galaxies is stretched as the universe expands. This stretching results in an increase in the wavelength of the light, shifting it towards the red end of the spectrum. The further away a galaxy is, the greater the redshift, which is indicative of the universe's expansion. This effect is fundamental in cosmology, as it provides evidence for the Big Bang theory and allows astronomers to determine the distances and velocities of galaxies relative to Earth.

The other options do not accurately describe the effects associated with cosmological redshift. For instance, the brightness of light is influenced by factors such as distance and the intrinsic luminosity of the source, rather than being directly increased by redshift. The relationship between wavelength and frequency is also relevant, as the increase in wavelength due to redshift inherently decreases frequency, but the question specifically poses the effects on light itself. Distortion of shape is not a characteristic effect of redshift; light waves undergo a change in wavelength and frequency without altering their fundamental shape. Thus, the stretching of wavelengths is the most direct and scientifically accurate description of the impact of cosmological redshift on light.