What is the term for the increase in the wavelength of electromagnetic waves emitted by a star due to its motion away from us?

The phenomenon of an increase in the wavelength of electromagnetic waves emitted by a star due to its motion away from an observer is known as red shift. This occurs because, as the star moves away, the waves of light it emits are stretched, resulting in a longer wavelength. In terms of the visible spectrum, this means that the light appears more red, hence the term "red shift."

Red shift is a critical concept in astrophysics and cosmology, as it provides evidence for the expansion of the universe. By measuring the red shift of light from distant galaxies, astronomers can determine how quickly those galaxies are receding from Earth, which helps to estimate their distance and the overall dynamics of the universe.

In contrast, other terms like blue shift refer to the decrease in wavelength (e.g., when an object is moving towards us), while options like sound shift and light wave shift do not accurately describe the specific phenomenon related to electromagnetic waves in this context.