|MadSci Network: Physics|
Hi, The simple answer is that neither wavelength (and thus frequency, since they are related) nor polarization of light is directly affected in most of the weak gravitational fields in which we observe lensing to occur. The changes we do observe relate to the time the lensed light takes to travel, the magnification of the light, the distortion of the shape of the light bundles, and the longer path-lengths travelled. However, in very strong gravitational fields (e.g. near a black hole or a compact neutron star) where the bending angles are large the light will experience a gravitational redshift and the observed wavelength would be shifted longwards (become redder). Finally, you can imagine scenarios where there is a net polarization or wavelength change observed, not by the lensing itself but because of secondary effects: for example if the magnification is not constant across the source and different parts are lensed more strongly than others, or if the light is reddened by passing through dust along the lensed light path. Meghan
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