Physic P1 - Waves

Physic P1 - Waves

1. BASICS

   • Made up of a series of oscillations or vibrations.
   • Wave speed/m/s = Frequency/Hz x Wavelength/m

2. ELECTROMAGNETIC WAVES

   • They don't need a medium to travel through
   • Travel in straight lines
   • Travel at 300,000,000 m/s

3. REFLECTION

   • Angle of incidence is always equal to the angle of reflection

4. REFRACTION

   • As waves enter a different medium their speed changes causing them to change direction
     • If it slows down it bends towards the normal, if it speeds up it bends away from the normal

5. DIFFRACTION

   • Whenever a wave passes through a gap or move around an obstacle they spread out
     • The longer the wavelength or the smaller the gap, the greater diffraction

6. TOTAL INTERNAL REFLECTION

   • When all of the light is reflected internally and stays within the glass.
   • Only happens if angle of incidence is greater than critical angle and if the light is travelling in the denser of the two materials.
   • Optic Fibres
     • Very fine glass cables which can be used to transmit large amounts of information or help doctors look inside their patient.
     • Waves travel along optic fibres by total internal reflection

7. COOKING

   • Infrared
     • Used in toaster as IR radiation is emitted by warm objects. The warmer an object is the more IR it emits. If an object aborbs IR radiation its surface gets hotter.
   • Microwave Ovens
     • Microwaves travel about 1 cm into the the food which are absorbed by the fat and water inside causing the food to heat up.
     • There are shiny metal surfaces which reflect microwaves so all parts of the food are heated
     • A metal mesh is placed inside the oven door to prevent micowaves escaping through glass or plastic and being absorbed by body tissue.

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