Q21P Consider a planar waveguide used... [FREE SOLUTION]

Chapter 20: Q21P (page 526)

Consider a planar waveguide used for attenuated total reflection measurement of a film coated on one surface of the waveguide. For a given angle of incidence, the sensitivity of attenuated total reflectance increases as the thickness of the waveguide decreases. Explain why. (The waveguide can be less than $1 渭尘$ thick.)

Expert verified

The rise in sensitivity of attenuated total reflectance as the waveguide thickness decreases.

The proportion of perpendicularly incident light reflected from a component relative to that reflected from a standard of established reflectance is known as reflectance.
A device (such as a duct, coaxial cable, or glass fibre) for confining and directing the propagation of electromagnetic waves (such as light), particularly a metal tube for channelling ultrahigh-frequency waves.

It is necessary to explain why the sensitivity of attenuated total reflectance increases as the waveguide thickness decreases.

The number of reflections inside increases as sensitivity increases, and the waveguide expands as well. Because each reflection has a certain amount of attenuation.
The number of reflections is inversely proportional to the waveguide at a constant angle of incidence.
As the waveguide shrinks, the number of reflections grows.