3.5 - Uses of Visible Light
Optical fibres carry visible light
Optical fibres are thin glass or plastic fibres that carry data over long distances as pulses of light.
How the light travels
- Light enters the narrow core at a shallow angle and bounces off the boundary with the outer cladding until it emerges at the far end.
- The light stays trapped inside the core by total internal reflection.
- Visible light is used because it's not easily absorbed or scattered as it travels.
Uses
- Telephone and broadband internet cables.
- Medicine - To see inside the body without surgery.
Cameras use visible light
A camera uses a lens to focus visible light onto a light-sensitive film or sensor, which records the image.
Controlling the light
- Lens aperture - Controls how much light enters the camera.
- Shutter speed - Controls how long the film or sensor is exposed to light.
- Sensor sensitivity - Controls how responsive the sensor or film is to light.
TermDefinition
Optical fibreA thin glass or plastic fibre that carries data over long distances as pulses of light or infrared radiation.
Total internal reflectionThe complete reflection of light back into a material when it meets a boundary with a material in which light travels faster (for example from glass into air), at an angle of incidence greater than the critical angle.