Florida Teacher Certification Examinations (FTCE) Subject Area Practice Test

What phenomenon describes the change in frequency of light when a source moves away from an observer?

1. Blue shift

2. Red shift

3. Green shift

4. Static shift

The correct answer is: Red shift

The phenomenon that describes the change in frequency of light when a source moves away from an observer is known as red shift. When an object emitting light moves away from an observer, the wavelengths of the light are stretched, resulting in a shift towards the red end of the spectrum, which is characterized by longer wavelengths. This effect is significant in astrophysics, where it has been used to measure the movement of galaxies, indicating that many are receding from us, which supports the theory of the expanding universe. In contrast to this, blue shift occurs when a light source moves toward an observer, resulting in shorter wavelengths, while green shift is not a commonly recognized term in physics. Static shift suggests a scenario where no movement occurs, making it irrelevant in this context. Understanding red shift provides valuable insight into cosmic phenomena and the dynamics of celestial objects.