When is the RI / NA combination correct?
When light passes from a dense medium (glass) into a less dense medium (water) <br>
total internal reflection occurs above a certain angle of incedence. High aperture objectives easily generate rays at angles beyond this limiting angle. <br>
When the refractive index of the medium is below the objective's NA this will occur.
Example: with an NA = 1.4 and a watery medium (refr. index slightly above 1.3), the most oblique rays cannot pass into the medium and will be totally reflected, effectively limiting the NA of the objective.
Huygens software with compute engines from 2.6.2 onwards will handle this situation gracefully; below that an error is reported.
See also: <br>
What does the message: 'total reflection at glass/medium interface (...)' mean?
See wiki article → Numerical Aperture.
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Keywords: numerical aperture NA refractive index internal reflection<br>
Categories: Faq Deconvolution, Faq Microscopy, Huygens Faq, Imported Faqs<br>
Platforms: Irix Linux Windows Mac AIX<br>
Related products: Hu Ess Hu Pro<br>
