Waves

Waves

Sound Waves
1. Longitudinal waves - vibrating objects
  1. travel to inner ear - eardrum - to hear it
2. Reflect & Refract
  1. reflected by hard flat surfaces
    1. rooms with carpet, furniture etc. absorb sound - stop echoes
      1. delay between original sound & echo - echo has to travel further
3. Higher Frequency = Higher Pitch
  1. frequency = complete vibrations each sec
  2. Bigger Amplitude = Louder
Basics
1. Amplitude = rest position to crest
2. Wavelength = full cycle of wave
3. Frequency = no. of complete waves passing certain point per second (Hz)
4. Transverse = sideways vibrations
  1. light & EM waves
  2. ripples on water
  3. Transverse Waves - waves = perpendicular to direction of energy transfer
  4. waves on strings
  5. slinky spring waved up and down
5. Longitudinal = same line vibrations
  1. sound waves & ultrasound
  2. shock waves
  3. slinky spring pushed
  4. Longitudinal = vibrations same direction as energy transfer
6. Speed = Frequency x Wavelength m/s = Hz x m
EM Waves & Uses
1. Microwaves - satellite communication & mobile phones
  1. need microwaves that can pass through Earth's watery atmosphere - radio waves can't
    1. signal transmitted into space - picked up by satellite orbiting - transmitted back to Earth - picked up by satellite dish
  2. mobile calls - microwaves - to nearest transmitter
    1. microwaves sometimes absorbed by water & heat them up - cells in body might cook - could damage health
2. Infrared Waves - remote controls & optical fibres
  1. remotes - emit patterns of infrared to send commands
  2. optical fibres e.g.phone lines - carry data quickly
    1. use both infrared & visible light - signal carried as pulses of light/infrared & reflected off core from one end of fibre to other
3. Visible Light - photography
  1. cameras use lens to focus visible light onto film/sensor
    1. lens aperture - controls how much light enters camera
      1. shutter speed - how long film/sensor exposed to light
Light
1. all waves reflect, refract, diffract
2. Reflection
  1. light travelling in same direction reflects from uneven surface, reflects in different angles
  2. light reflecting from even surface (smooth & shiny), reflected at same angle with clear reflection
  3. Angle of INCIDENCE = Angle of REFLECTION
3. Diffraction
  1. waves spread out - through gap/pass obstacle
    1. narrower gap/longer wavelength = more the wave spreads
    2. gap similar to wavelength = lots of diffraction e.g. sound through door
    3. gap bigger than wavelength = little spreading e.g. light through door
4. Refraction - changing speed of a wave changes its direction
  1. waves only refract if they meet new medium at an angle
EM Waves & Communication
1. Remember My Instructions Visible Under X-Ray Glasses
  1. wavelength = 10ˉ¹⁵m to more than 10⁴m
  2. travel at same speed in vacuum
  3. higher frequency = shorter wavelength
2. Radio Waves = Communication
  1. long-wave radio wavelengths can diffract around hills, into tunnels - receiver doen't need to be in line of sight of transmitter
  2. short-wave radio signals (10m-100m) - can be received at long distances - reflect from ionosphere (electrically charged layer)
  3. TV & FM radio = short wavelengths - have to be in direct sight
Origins of the Universe
1. Universe = Expanding
  1. Galaxies light = red-shifted
    1. chemical elements - absorb different frequencies
      1. produce specific pattern of dark lines at frequencies it absorbs (on visible spectrum)
        light from galaxies - same patterns at lower frequency - towards red end
  2. Doppler Effect
    1. Something moving towards you - frequency seems higher/wavelength seems shorter
    2. Longitudinal & Transverse
  3. Further Away Galaxy = Greater Red-Shift
    1. all galaxies = moving away from us
      1. more distant galaxies = moving away faster
2. Big Bang - 14 billion years ago
  1. 'Steady State' theory - universe has always been/will be the same
    1. cosmic microwave background radiation (CMBR) = leftover energy from Big Bang - strong evidence
      1. low frequency electromagnetic radiation coming from all parts of universe
        after Big Bang, universe was very hot - everything emitted high frequency radiation
        as universe expanded, its cooled - now microwave radiation
3. Limitations
  1. universe expansion should be slowing down but actually - speeding up
  2. what caused explosion/conditions before

	Created by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

	Copied by vina_56 over 10 years ago

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