Fibre optic cable
A fibre optic cable is a long stretch of thin glass.
It’s used to transmit information - e.g. in the internet.
How it works
- The angle of incidence of each transmitted pulse of light must be greater than the critical angle.
- When light hits the edge of the fibre, it reflects. That’s because the angle is more than the critical angle, and so total internal reflection occurs.
- It’s not a ‘mirror’, but does still reflect (almost) all light.
Parts of a fibre-optic cable
- The core (the middle bit) has the highest refractive index
- The cladding (outside) has a slightly lower refractive index than the core (but still higher than air)
- The air around the cable has the lowest refractive index, around
1 .