P1d-light And Lasers Flashcards
Why is morse code a digital signal?
The light pulse is only either on or off
How was light used as a means of communication?
Signals sent in the form of morse code which is a series of on off signals
Signals relayed between stations to cover larger distances
What are the advantages of using light, radio and electrical signals for communication?
Travels fast
Electrical wires carry loads of info very quickly
Secure inside a cable
Portable
What are the disadvantages of using light,radio and electrical signals for communication?
Radio signals travel through the air can be intercepted
Cables difficult to repair
Signal strength depends on location
Where does total internal reflection happen?
Glass air boundary
Water air boundary
Perspex air boundary
How do optical fibres?
Carry data over long distances as pulses of light or infrared radiation
Ray of light enters fibre so that it hits the boundary between core and outer cladding at an angle greater than the critical angle for the material which causes TOR of ray within core
What happens if the angle of incidence is less than the critical angle?
Most of light is refracted into outer layer
Some is internally reflected
What happens if angle of incidence is equal to the critical angle?
Ray would go along the surface with a bit of internal reflection
What happens if the angle of incidence is greater than the critical angle?
No light comes out
All internally reflected
Eg
TIR
What are lasers used for?
Surgery Dental treatment Cutting materials in industry Weapon guidance Laser light shows
What does a laser produce?
A narrow beam of light of a single colour(monochromatic)
Why do lasers produce an intense coherent beam of light?
Waves have the same frequency
Waves are in phases with each other
Waves have low divergence
How is a laser beam used in a CD player?
- Reflection from shiny surface
- Information stored on bottom surface
- Information stored digitally
- Information in the form of pattern of bumps
- A CD will contain billions of pits
