The change in frequency of light emitted from an object when its light approaches an observer is known as what?

The phenomenon where the frequency of light emitted from an object increases as it approaches an observer is referred to as a blue shift. This occurs because the wavelengths of the light waves are compressed due to the motion of the emitting object towards the observer. The increase in frequency results in a shift of the light towards the blue end of the spectrum, which indicates higher energy and shorter wavelengths.

Red shift, on the other hand, happens when the light source moves away from the observer, leading to a stretching of the wavelengths and a decrease in frequency. Therefore, while red shift might be a common term discussed in the context of galaxies moving away from Earth, it does not apply here since the question specifically addresses the scenario where the light is approaching an observer.

The options of electromagnetic shift and light shift are not standard terminology used in physics to describe changes in light frequency due to motion, making them less relevant in this context. Thus, the correct answer highlights the specific nature of the frequency change when light approaches an observer.