gen-briefly-explain-the-doppler-shift-in-spectra-and-one-common-b546

Briefly explain the Doppler shift in spectra and one common misconception about it.

## Doppler Shift in Spectra The Doppler shift occurs when the wavelength of light from a moving object appears shifted relative to a stationary source. When an object moves **toward** us, its light is compressed to shorter (bluer) wavelengths—called **blueshift**. When moving **away**, the light is stretched to longer (redder) wavelengths—called **redshift**. The amount of shift is proportional to the object's velocity along our line of sight. ## Common Misconception **Misconception**: *Redshift means the object looks red, or that all its light shifts into the red part of the spectrum.* **Reality**: The entire spectrum shifts together. A blue spectral line just moves slightly toward the red end of the spectrum—it doesn't necessarily become actually red. Similarly, infrared lines shift further into the infrared. The object's overall color might not change noticeably unless the velocity is extremely high. We detect Doppler shifts by measuring how specific spectral lines (like hydrogen absorption lines) move from their expected "rest" wavelengths, not by the object's apparent color.