Total Internal Reflection Flashcards
How can light be sent along optical fibres?
Using Total Internal Reflection
What do optical fibres do?
Carry visible light over long distances
How do optical fibres work?
By Total Internal Reflection
They work by bouncing waves off the sides of a thin inner core of glass or plastic. The wave enters one end of the fibre and is reflected repeatedly until it emerges at the other end
Total Internal Reflection can only happen when…
A wave travels through a dense substance (like glass or water) towards a less dense substance (like air)
Total Internal Reflection depends on whether the [ ] is bigger than the [ ].
angle of incidence
critical angle
How are the angle of incidence and reflection measured?
From a normal
If the angle of incidence is less than the critical angle…
Most of the light passes out but a little bit of it is internally reflected. (Draw a diagram)
If the angle of incidence is equal to the critical angle…
The emerging ray comes out along the surface. There’s quite a bit of internal reflection
If the angle of incidence is greater than the critical angle…
No light comes out. It’s all internally reflected = total internal reflection
The value of the critical angle depends on the [ ]
Refractive Index
A [ ] material with a [ ] refractive index has a low critical angle.
dense
high
If a material has a high refractive index, it will totally internally reflect [ ] light - more light will be [ ] at an angle [ ] than the critical angle
more
incident
bigger
What is the formula including refractive index and critical angle ?
Refractive Index = 1 / SinC
What is a medical use of optical fibres?
Endoscopes
What is an endoscope?
A thin tube containing optical fibres that lets surgeons examine inside the body
