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Relative to the observer, the objected, emitting visible light will appear red in color because the wavelength of light is stretched hence acquiring longer wavelength in the visible electromagnetic spectrum (remember red light has the longest wavelength in the visible light spectrum).
Explanation:
Conversely, if the object was moving towards the observer, it would appear blue in color (blue shift) because the relative wavelength of the visible light would be ‘compressed’ (remember this is always relative to the observer) hence the wavelength would be shorter (and blue light has the shortest wavelength in the visible light spectrum).
Both these phenomenons are classified under Doppler shift effect of waves. It also occurs in our daily lives. When a wailing ambulance approaches you, the pitch of the wailing sounds is higher (relative to you). However, when the ambulance passes you and begins stretching away from you, the pitch of the wailing goes low.
Learn More:
For more on Doppler shift effect check out;
https://brainly.com/question/3841958
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