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2 public questions tagged with this topic.

Microscopy

Which microscopy uses a Nomarski prism?

Differential interference contrast depends critically on prisms that manipulate polarized light. A Nomarski prism, a modified Wollaston prism, splits plane-polarized illumination into two orthogonally polarized beams with slight lateral shear, typically less than resolution limit. After passing through specimen regions with different refractive indices, the beams acquire phase differences. A second Nomarski prism above objective recombines them, and analyzer converts phase gradients into intensity differences. This design yields high-contrast, pseudo-relief images highlighting membrane edges, nuclei and contractile vacuoles in live unstained protozoa and developing embryos.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Microscopy

Which microscopy uses heavy metals for contrast?

Transmission electron microscopy images ultrathin biological sections using electrons rather than photons. Because biological material consists mainly of light atoms that scatter electrons weakly, contrast must be enhanced with heavy metals. Osmium tetroxide fixes lipids and adds electron density, uranyl acetate binds nucleic acids and proteins, and lead citrate stains membranes and ribosomes. These high atomic number atoms scatter incident electrons strongly, creating dark regions in bright-field TEM images. Staining thus reveals bilayer membranes, chromatin texture and viral particles at nanometer resolution unattainable with visible light microscopes.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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