In earlier post I had written "at the subject", thinking in a moment of craziness that we were dealing with diatoms that were dry versus immersed.rjlittlefield wrote: ↑Thu Jun 02, 2022 10:11 amAnother possible factor: at same NA, the light cones ** *** ******* will be narrower, in proportion to the RI of the immersion fluid.
So where NA 0.95 requires light rays that are angled at 71.8 degrees off-axis, NA 1.0 in RI 1.51 requires only 41.5 degrees off axis.
But even with subjects mounted under coverslips, those angles apply for light between the coverslip and the objective.
Intuitively, it seems like this should make the immersion objective simpler to design and manufacture, since the dry objective has to bend the light more while maintaining the same accuracy in optical path length for all rays.
--Rik