P1 9,10,11,12

P1 9,10,11,12

1. P1 9: Total internal reflection and fibre optics

   • only happens when angle of light greater than critical angle
     • light is travelling in the denser of the two materials
   • fibre optics are very fine glass cables
   • help doctors look inside the body without cutting the patient open
   • also used in broadbands

2. P1 10: using light

   • light can be used for communication
     • e.g morse code
   • lasers
     • lasers can be used in: surgery and dental treatment, guiding weapons, cd and dvd players and cutting materials e.g steel plates

3. P1 11: cooking with waves

   • if objects absorbs infrared radiation its surface gets hotter
   • when microwaves or toasters are used the emit infrared heat
     • microwaves have a rotating plate so the heat gets spread easily
       • its made out of metal so heat reflects of the sides
       • Mesh door so infrared doesn't burn human skin

4. P1 12: communicating with waves

   • phones send and receive microwaves
   • when you talk the sound is turned into a microwave signal thats sent to the nearest mast
   • to get signal you need to be fairly close to a mast
   • People are concerned that the microwave signals will affect our brains

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