What phenomenon occurs to light from distant stars as the universe expands?

As the universe expands, the phenomenon that occurs to light from distant stars is known as redshift. This effect happens due to the stretching of space itself, which results in wavelengths of light being elongated as they travel through the expanding universe.

When light waves are emitted from a star, if the universe is expanding, the distance between the source of the light and the observer increases over time. This increase in distance causes the wavelengths of light to stretch, moving them towards the red end of the spectrum, hence the term "redshift." The greater the distance a star is from us, the more its light is redshifted, which is an important observational tool in astrophysics for understanding the rate of the universe's expansion and the distance of celestial objects.

In contrast, reflection pertains to light bouncing off surfaces, acceleration implies an increase in speed rather than a change in wavelength, and refraction involves the bending of light as it passes through different mediums. None of these processes describe the effect of the universe's expansion on light from distant stars.