If light goes through a regular glass lens, it will disperse. As shown in this pic:
In our observation of light through gravitational lensing, is there any frequency changed in Light/EM wave after the lensing effect? Some claimed there is blue shift. Can anyone confirm that with supporting data?
Thank you in advance.

In our observation of light through gravitational lensing, is there any frequency changed in Light/EM wave after the lensing effect? Some claimed there is blue shift. Can anyone confirm that with supporting data?
Thank you in advance.
