The Telephone

transmitterloudspeaker

(Sound energy to electrical energy)

(Electrical energy to sound energy)

Printed circuit board of the telephone

An Older Telephone

Using an oscilloscope1) 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

4) Ray gets internally reflected

3) Ray still gets refracted (just!)

2) Ray still gets refracted

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.