Physics 1

Physics 1

1. Waves

   • waves are vibrations that transfer energy from place to place
   • Some waves travel through a substance (medium)
     • Sound and seismic waves
       • is the medium that vibrates
     • no medium
       • electromagnetic radiation waves
         • electric and magnetic fields vibrate
   • Transverse waves
     • oscillations perpendicular to energy direction
     • travel at the same speed through a vacuum
   • longitudinal waves
     • oscillations are parallel
       • sound waves
     • show compression ||||
     • refraction || |
   • frequency (Hz)
     • num of waves per second
     • wave speed = frequency X wavelength
   • reflection
     • angle of incidence = angle of reflection
     • laterally inverted
       • mirror: left=right
     • Echoes are reflection of sound
       • greater aplitude =louder greater frequency=higher pitch
   • hearing
     • human range 20Hz-20kHz
       • above 20kHz = ultrasound
   • electromagnetic spectrum
     • white light>prism = spectrum (refraction)
     • Radio/microwaves =communication
       • diffractions allows low frequency waves to be received behind hills
       • ionsphere
         • radio waves reflected from electrical charged layer of atmosphere
       • microwaves:mobile phones
         • tansmitters and receivers on buildings
     • infrared- feel but no see (toasters)
       • transmit info from place to place
         • remote

2. Big bang

   • cosmic background radiation; heat left over from explosion
     • microwaves coming from every direction in space
       • evidence
         • light from other galaxies is red
           • further away=more red shifted

3. Doppler effect

   • change in frequency and wave length
     • closer=wave length decrease+frequency increase

4. Redshift

   • sun contains helium:black line in spectrum
   • the further a star is the more light it redshifted
     • distant galaxies movies away from us
       • the further away the faster its moving
         • gradually expanding universe
           • everything is moving away from each other