Transcript 0413totalinternalreflection.ppt.pptx

Total Internal Reflection
Total Internal Reflection
• When light passes from one material into a
second material where the index of refraction
is less, the light bends away from the normal.
At a particular incident angle, the angle of
refraction would be 90 degrees and the
refracted ray would skim along the surface. At
angles of incidence greater than the critical
angle the light would be totally internally
reflected.
Critical Angle
• Sin (critical angle) = n(2)/n(1)
– For angles less than the critical angle, the light
would be refracted.
– For the critical angle, the light would skim along
the boundary.
– For angles greater than the critical angle, the light
would be totally internally reflected.
Example
• For the air-water interface determine the
critical angle
– Sin(critical angle) = n(2)/n(1) = 1.0/1.33 = 0.75
– Sin 49 degrees = 0.75
– The critical angle for the air-water interface is 49
degrees.
Example
• For the air-glass interface determine the
critical angle
– Sin(critical angle) = n(2)/n(1) = 1/1.50 = .67
– Arcsin (0.67) = 42 degrees
– At angles less than 42 degrees light will be
refracted. At 42 degrees light will skim along the
boundary. At angles greater than 42 degrees light
will be totally internally reflected.
Fiber optics
• Glass and plastic fibers
• Extremely narrow fibers can be used
• Light can be transmitted along it with almost
no loss because of total internal reflection
Applications of fiber optics
• 1. telecommunications (verizon Fios)
• Telephone calls, video signals, computer broadband
• 2. Medicine
• Fiber optics used to transmit clear picture
• Examples: bronchoscope, colonoscopes, endoscopes