The Doppler Effect is a phenomenon that occurs when a sound or light source moves relative to an observer. When the source approaches, the waves compress, resulting in a higher frequency or pitch, while moving away causes the waves to stretch, leading to a lower frequency or pitch. This effect is commonly experienced with passing sirens or trains. In addition to sound, the Doppler Effect also applies to light. When a star moves toward Earth, its light shifts to the blue end of the spectrum, known as blue shift. Conversely, if it moves away, the light shifts to the red end, called red shift. This principle helps astronomers measure the speed and direction of celestial objects.