Total Internal Reflection

Question 1

Critical angle

Answer 1

The angle that if the angle of incidence = critical angle, the angle of refraction = 90 degrees

Question 2

Total Internal Reflection

Answer 2

The angle of incidence exceeds the critical angle (only if going from more to less dense medium)

Question 3

Why do diamonds sparkle?

Answer 3

It has a high refractive index so separates colours more than other materials. Also has a low critical angle so the light can be totally internally reflected multiple times before exiting

Question 4

How do optical fibres work

Answer 4

They Totally Internally reflects light each time it hits the boundary between the core and cladding even if the fibre is bent.

Question 5

Why is there cladding on optical fibres

Answer 5

To prevent light / signals crossing between two cores as that would happen without cladding

Question 6

Why are optical fibres narrow

Answer 6

Prevents modal dispersion where a direct transmission travels a shorter distance than one with TIR and might merge with the next pulse

Question 7

How does an endoscope work

Answer 7

Contains two bundles of fibres. Inserted into your body and illuminated using light sent through one of the fibre bundles. A lens over the other fibre bundle forms an image. The light that forms this image travels down the fibre to the observer. These need to a coherent bundle.

Question 8

Coherent bundle

Answer 8

Fibres at each end need to be in the same relative positions