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P1d: Lights and Lasers
- Morse Code
- The Morse code uses a series of dots and dashes to represent letters of the
alphabet. ––This code is used by signalling lamps as a series of short and
long flashes of light.––It is an example of a digital signal.
- The Morse code uses a series of dots and dashes to represent letters of the
alphabet. ––This code is used by signalling lamps as a series of short and
long flashes of light.––It is an example of a digital signal.
- Laser Light
- White light is made up of different
colours of different frequencies
out of phase.
- Laser light has only a single
frequency, is in phase and shows
low divergence.
- Laser light is used to read from the
surface of a compact disc (CD): ––the
surface of the CD is pitted ––the pits
represent the digital signal ––laser light
is shone onto the CD surface and the
difference in the reflection provides the
information for the digital signal.
- White light is made up of different
colours of different frequencies
out of phase.
- Sending Signals
- When a signal is sent by light, electricity,
microwaves or radio, it is almost
instantaneous.
- Each method of transmission has
advantages and disadvantages: ––can
the signal be seen by others? ––can
wires be cut? ––how far does the
signal have to travel?
- When a signal is sent by light, electricity,
microwaves or radio, it is almost
instantaneous.
- Critical Angle
- When the angle of refraction is 90°, the
angle of incidence is called the critical
angle.
- Some fibres are
coated to improve
reflection.
- If it is passing from a more dense material
into a less dense, the angle of refraction is
larger than the angle of incidence.
- When light travels from one material
to another, it is normally refracted
- Telephone conversations and computer data are
transmitted long distances along optical fibres at the
speed of light (200 000 km/s in glass).
- If the angle of incidence is bigger than the critical angle, the light is
reflected: ––this is total internal reflection.
- When the angle of refraction is 90°, the
angle of incidence is called the critical
angle.
- Endoscopy
- An endoscope allows doctors to see inside a body
without the need for surgery. ––Light passes along
one set of optical fibres to illuminate the inside of the
body. ––The light is reflected. ––The reflected light
passes up another set of fibres to an eyepiece or
camera.
- An endoscope allows doctors to see inside a body
without the need for surgery. ––Light passes along
one set of optical fibres to illuminate the inside of the
body. ––The light is reflected. ––The reflected light
passes up another set of fibres to an eyepiece or
camera.
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