Page 100 - Big Ideas Year 9 sciPAD 2025

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100 SCIPAD - BIG IDEAS - BOOK 1
THE IMPORTANCE OF WAVES
Using Reflection - Fibre Optics
An optical fibre is a thin fibre of glass or clear plastic that can carry light from one end to the
other. The study of optical fibres is called fibre optics.
Optical fibres enable the transmission of large amounts of information over greater distances
and at quicker speeds than traditional copper wires.
An optical fibre is a long, flexible, transparent cable with a very small diameter. When light
enters one end it is totally internally reflected (no light escapes or bounces backwards) along
its entire length, until it emerges at the other end.
Fibre-optic cables contain the optical fibre in their core. Around the core is a layer called the
cladding. The core and cladding are made of different kinds of glass or plastic. If the cladding
of the fibre is scratched, it may break. A plastic coating called the buffer covers the cladding
to protect it. Often, the buffered fibre is put inside an even tougher layer, called the jacket. This
makes it easy to use the fibre without breaking it.
The main use of optical fibre is in long-distance communication (telecommunication). Since the
light does not leak out of the fibre as it travels, the light can go a long distance before the signal
gets too weak to be useful. They can be used to send telephone and internet signals between
cities. Fibre-optic cables are also unable to be ‘tapped’ (i.e. listened to by others). Fibre-optic
cable is lighter than traditional copper wire so it easier and cheaper to transport and lay.
These fibres are also used to carry light for humans to see. This is sometimes used for decoration,
like fibre-optic Christmas trees. Sometimes it is used for lighting when it is convenient to have the
light bulb somewhere other than where the light needs to be. This is sometimes used in signs and
art for special effects.
A bundle of fibres can be used to make a device called an endoscope. This is a long thin probe
that can be put into a small hole, and will send an image of what is inside through the fibre to
a camera. Endoscopes are used by doctors to see inside the human body, and are sometimes
used by engineers to see inside tight spaces in machines.
Light ray enters
optic fibre
Light ray exits
optic fibre Light is totally internally
reflected along optic fibre
1. Describe an optical fibre. 

2. Outline three advantage of using optical fibres for telecommunications (phone lines and
internet). 


3. State two other uses for optical fibres. 

4. Label the diagram of a fibre-optic cable shown below.
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