The Telephone
loudspeaker (Electrical energy to sound energy)
transmitter (Sound energy to electrical energy)
Printed circuit board of the telephone
An Older Telephone
Using an oscilloscope
1) Quiet sound, low frequency:
2) Quiet sound, high frequency:
3) Loud sound, low frequency:
4) Loud sound, high frequency:
Telecommunication Optical Fibres
• The law of reflection. • When a ray of light bounces off a mirror , the angle going in equals the angle coming out. • The line at right angles to the mirror is called the normal.
Optical Fibres
• When light is incident on a glass surface, refraction or bending of the light takes place. • The light comes out of the glass. • This however is dependent on the angle i.
Finding the Critical Angle… 1) Ray gets refracted 2) Ray still gets refracted
3) Ray still gets refracted (just!)
4) Ray gets internally reflected
THE CRITICAL ANGLE
Optical Fibres
• Optical fibres are made of thin flexible glass threads. • They are about the size of a human hair. • The fibres have a protective coating which keeps the light inside the fibre.
Satellites
• Interactive summary. • Satellites which orbit the earth every 24____ are called ________ satellites. • They are above the _____ point on the _____ . • Satellites use ______ dishes to _______ the microwave signals. • The microwave signals travel in _______ lines.