A total internal reflection fluorescence microscope illuminates a sample through a…

PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Macromolecules, membranes and cell architecture · Molecular machines, transport and bioenergetics

Forces, Machines and Signals, Ch Measuring one molecule: traps, tweezers and single-molecule fluorescence

Problem

A total internal reflection fluorescence microscope illuminates a sample through a glass coverslip of refractive index n1=1.518n_1 = 1.518 in contact with water of refractive index n2=1.33n_2 = 1.33, using an argon-ion laser line of wavelength λ=488 nm\lambda = 488\,\mathrm{nm} at an incidence angle θ=68∘\theta = 68^\circ (measured from the normal, greater than the critical angle). ((a)) Compute the penetration depth dd of the evanescent excitation field into the water. ((b)) State what determines whether a fluorophore near the surface is excited, in terms of dd.

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