Calculating Penetration Depth for TIR of Evanescent Waves at Glass-Air Interface

[lcr2139]

Homework Statement

: Calculate the penetration depth of an evanescent wave undergoing TIR from glass (n = 1.5) to air interface, such that the amplitute is reduced to 1/e times its original value. Wavelength of the incident light is 5000 angstroms and 60 degrees. First make sure that incident angle of 60 degrees produces TIR - the critical angle is less than 60 degrees.[/B]

Homework Equations

The Attempt at a Solution

I proved that the critical angle is less than 60 degrees. How does that relate to penetration depth and the amplitute of the evenescent wave?[/B]

 

[Dr. Courtney]

Try writing down a few of the equations. Drawing a picture can help also.