PHYSICS ...

PHYSICS ...

1. lenses

   • A lens is transparent block that causes light to refract (changes the direction the light travels in). A converging lens (or convex lens) is curved on both sides. This means the light rays coming out of it come together at a point – they converge.

2. waves..and eletromagnet spectrum

   • what are waves?
     • Waves are vibrations that transfer energy from place to place without matter - solid, liquid or gas
   • longitudinal waves
     • vibrations are along the SAME direction as the wave is travelling
   • transverse waves
     • the vibrations are at 90 degrees to the direction of travel of wave
   • How fast do waves travel? The speed of a wave - its wave speed - is related to its frequency and wavelength, according to this equation:
     • wave speed (metre per second) = frequency (hertz) × wavelength (metre
   • ELECTROMAGNET
     • Hazards of electromagnetic radiation
       • microwaves cause internal heating of body tissues
       • infrared radiation is felt as heat and causes skin burns
       • X-rays damage cells, causing mutations (which may lead to cancer) and cell death
       • gamma rays also damage cells, causing mutations (which may lead to cancer) and cell death.
     • radio , microwave, infrared , visible ,ultraviolet,xrays,gamma ray
     • radiowaves broadcasting communications satellite transmissions Satellite with solar panels in earth orbit microwaves cooking communications satellite transmissions A microwave infrared cooking thermal imaging short range communications optical fibres television remote controls security systems A remote control visible light vision photography illumination A camera ultraviolet security marking fluorescent lamps detecting forged bank notes disinfecting water Counterfeit money detection X-rays observing the internal structure of objects airport security scanners medical X-rays X-ray of hands. Credit: Ron Chapple gamma rays sterilising food and medical equipment detection of cancer and its treatment

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