The Doppler effect is a phenomenon observed when there is relative motion between a wave source and an observer. It causes a shift in the frequency of the wave as perceived by the observer. The Doppler effect can occur with both sound waves and light waves, but there are some differences in how it manifests for each.
For sound waves, the Doppler effect is commonly experienced in everyday situations. When a sound source, such as a moving vehicle, approaches an observer, the sound waves get compressed, resulting in a higher frequency or pitch. Conversely, when the sound source moves away from the observer, the sound waves get stretched, leading to a lower frequency or pitch.
In the case of light waves, the Doppler effect can also occur due to relative motion between a light source and an observer. However, the effect is more commonly observed in astronomical contexts where there are significant velocities involved, such as when celestial objects move relative to Earth.
The Doppler effect for light is often referred to as the "redshift" or "blueshift" depending on whether the light is shifted towards longer (red) wavelengths or shorter (blue) wavelengths. When a light source moves away from an observer, the wavelengths of the light appear to stretch or shift towards the red end of the spectrum, resulting in a redshift. Conversely, when a light source moves towards an observer, the wavelengths appear compressed or shifted towards the blue end of the spectrum, leading to a blueshift.
The Doppler effect for light waves has been instrumental in astronomy for studying the motion of stars, galaxies, and other celestial objects. It has provided insights into the expansion of the universe, the movement of galaxies, and the presence of exoplanets, among other phenomena.
In summary, the Doppler effect occurs for both sound waves and light waves. For sound waves, it affects the perceived pitch due to compression or stretching of the waves. For light waves, it causes a shift in the wavelength towards red or blue, known as redshift or blueshift, respectively, due to the relative motion between the light source and observer.