Total Internal Reflection Flashcards
What do optical fibres do?
Carry visible light over long distances
How do optical fibres work?
They bounce waves off the sides of a thin inner core of glass and plastic
Wave enters one end of fibre and is reflected repeatedly until it emerges at the other end
Why do optical fibres work?
Because of total internal reflection
When can total internal reflection happen?
When a wave travels though a dense substance like glass or water toward a less dense substance like air
What happens if the angle of incidence is less than the critical angle?
Most of light passes out but a little bit it internally reflected
What happens if the angle of incidence is equal to the critical angle?
The emerging ray comes out along the surface and there’s quite a bit of internal reflection
What happens if the angle of incidence is greater than the critical angle?
No light comes out and it’s all internally reflected
I.e total internal reflection
Where are the angle of incidence and the angle of reflection always measured from?
The normal
These two angles are always equal
What does a dense material with a high refractive index have?
A low critical angle
What formula links refractive index and critical angle?
Refractive index = 1/ sin C
What is an endoscope?
A think tube containing optical fibres that allow surgeons to examine inside the body
How do endoscopes work?
One bundle of optical fibres carry light to area of interest while another carries an image back to be viewed
Image can be seen through eyepiece or in a screen
What an advantage of using endoscopes?
They can now perform many operations by only cutting small holes (key hold surgery)
