Gravitational lensing does not produce a detectable red or blue shift in light deflected by massive bodies, as confirmed by current observations. While photons passing near a massive object may theoretically lose energy due to tidal effects, this impact is negligible. The net effect of gravitational lensing typically results in a balance between blueshift and redshift, leading to no significant frequency shift. However, variations can occur if the gravitational potential changes during the light's traversal, particularly with large objects like galaxies.
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jollett said:Hi I'm new to the forums. I have a question I hope you guys can help me understand. When gravitational lensing produces multiple images of the same object, do they undergo any red/blue shift? And if so, is the frequency shift the same for each image?
meopemuk said:No, there is no red/blue shift of light deflected by a massive body. At least, nothing of that sort has been observed. In principle, one can expect that photons passing near a massive body should lose a part of their energy (and frequency) due to the tidal effect. However, this effect is very small.
Eugene.
Matterwave said:Usually, for gravitational lensing, the blueshift incurred while the light is "dropping into" the gravitational potential matches the redshift incurred while the light is escaping from the gravitational potential, so that the net effect is 0. This is not true if the gravitational potential changes during the time light is traversing the object. I think this happens when light is lensed by a very large object (e.g. a galaxy) rather than like a star, but I'm not sure. I do know that the anisotropies in the CMB are due to this effect (there's a paper on it, but I forget by who).