p1 d-f

p1 d-f

1. d

   • 1. Using light increases the speed of communication
   • 3. Total Internal Reflection occurs when the angle of incidence is bigger than the critical angle for the materials
   • 4. If the angle of incidence is too small the light will leave the material rather than staying inside.
   • 5. Lasers produce an intense, narrow beam of light of a single colour (monochromatic).
   • 6. The waves in a laser beam are coherent, which means they are all in phase.
   • 7. Lasers can be used in surgery and dental treatment, for cutting materials in industry, weapon guidance and in laser light shows
   • 8. Morse code is a series of on off signals, which means it is digital
   • 2. Total internal reflection is when a wave stays inside a material by bouncing off the internal walls.

2. e

   • 9. Microwaves are absorbed only by water and fat in the outer layers of the food increasing their KE.
   • 7. Properties of microwave radiation include: they penetrate (about 1cm) into food, are reflected by shiny metal surfaces, can cause burns when absorbed by body tissue and can pass through glass and plastics.
   • 5. Infrared is absorbed only by particles on the surface of the food increasing their energy.
     • 6. This energy is then transferred to the rest of the food by conduction and convection.
   • 4. Properties of infrared radiation include: heats the surface of the food and is reflected by shiny surfaces.
   • 2. The worst emitters and absorbers (and so best reflectors) are shiny and white.
   • 1. The best emitters and absorbers are dull and black.
   • 8. Water and fat absorb microwaves
   • 3. Mobile phones use microwave signals
   • 10. When microwaves transmit information there is some signal loss due to interference, the curvature of the earth, no diffraction around objects and adverse weather.
   • 11. The evidence of dangers from mobiles is not conclusive 12. Therefore it is not easy to decide on the siting of phone masts
     • 13. As you increase the frequency of a microwave the energy increases

3. f

   • 1. Analogue signals have a continuously variable value
     • 2. Digital signals are either on (1) or off (0
   • 3. Everyday uses of infrared radiation include: remote controls and short distance data links.
     • 4. Infrared sensors detect body heat
   • 5. The advantages of using digital signals include: that it is easier to remove noise and you can use multiplexing.
     • 6. Multiplexing is when you send more than one signal on a carrier wave.
   • 7. The advantages of using optical fibres include: multiplexing and lack of interference in the final signal