Interactive applet Fun with Snells Law Same applet

Interactive applet: Fun with Snell’s Law. Same applet as slide 20, try glass into water.

Total Internal Reflection; Fiber Optics Suppose n 2<n 1. The largest possible value of sin( 2) is 1 (when 2 = 90). The largest possible value of sin( 1) is For 1 larger than this, Snell’s Law cannot be satisfied! Example: =1. 5 n 2=1 sin angle, 2=0. 667 sin of 2. This valuen 1 of isand called thethen critical C. sin. For any angle 1=1/1. 5 If you set larger then Cn, 1 all sin of 1=n has no solution. A ray incidence than the 2 sin light 2 incident at an interface 1=45 , coming in at and a 45 none angleis cannot pass through the interface and be is reflected, transmitted. refracted.

1 < C 1 close to C 1 1 1 > C 1

n 2 n 1>n 2 Ray incident normal to surface is not “bent. ” Some is reflected, some is transmitted.

n 2 Increasing angle of incidence… n 1>n 2

n 2 Increasing angle of incidence…more… n 1>n 2

n 2 n 1>n 2 Increasing angle of incidence…more…critical angle reached… some of incident energy is reflected, some is “transmitted along the boundary layer.

n 2 n 1>n 2 Light incident at any angle beyond C is totally internally reflected.

application: fiber optics http: //laser. physics. sunysb. edu/~wise/wise 187/janfeb 2001/reports/and rea/report. html