Waves

• Waves transfer


  energy without transferring matter
• λ

  - wavelength

  - crest to crest

  
• A

  - amplitude

  - maximum displacement from equibrillium (x-axis)

  
• f

  - frequency

  - measured in Hz

  
• frequency equation


  f = 1/t
• speed of wave equation


  v = f λ
• transverse waves


  - oscillations are PERPENDICULAR to the direction of energy transfer

  - most waves (e.g. EM waves, water ripples)

  
• longitudinal waves


  - oscillations PARALLEL to the direction of energy transfer

  - e.g. sound waves, p waves (shock waves)

  
• when light hits a material it gets...

  - reflected

  - absorbed (transfers energy)

  - transmitted (keeps travelling)
• incident angle


  - between the incoming ray and normal

  - equal to the reflected angle
• normal

  - perpendicular to the point of incidence (where the incoming ray hits the boundary)

  - different for EVERY ray
• specular reflection


  - single direction

  - smooth surface

  - results in a clear image

  
• diffuse reflection

  - scattered rays in different directions

  - rough surface

  - results in an unclear image, matte surface

  
• refraction

  - change in direction between mediums

  - caused by a change in speed
• in dense mediums light travels...


  slower
• light travelling from less dense to a more dense medium...

  makes it bend towards the normal
• concave lens


  - caves inwards

  - diverges the light

  
• convex lens


  - bulges outwards

  - converges the light

  
• high power lenses


  - the lens is more curved
• real images


  light comes together to form an image that can be captured on a screen
• virtual images


  - object appears to be coming from a different place

  - represented with a dashed line
• describing ray diagrams


  - real/virtual

  - upright/inverted

  - larger/diminished
• EM spectrum


  radio, microwaves, infrared, visible light, UV, xrays, gamma
• Radio waves


  - 1 - 10⁴m

  - low frequency: not damaging

  - used in AC currents, oscillating magnetic and electric fields, communication

  - shortest waves: don't bend, used for TV/FM radio

  - short waves: reflect off ionsphere

  - long waves: signals across earth

  
• Microwaves


  - 10⁻² m

  - used for: satellites, microwave ovens

  - can travel through watery atmosphere

  - water in food absorbs waves and energy is transferred
• Infrared


  - 10⁻⁵ m

  - given out by all hot objects

  - used in: electric heaters, IR cameras, toasters
• Visible light


  - 10⁻⁷ m

  - used in: fibre optic cables

  - can be refracted: won't get lost when refracted

  - ROYGBIV spectrum

  
• UV light


  - 10⁻⁸ m

  - used in florescent lights

  - energy efficient

  - given out by the sun
• XRays


  - 10⁻¹⁰ m

  - pass through flesh but not denser materials

  - can be used for cancer treatment

  - high dose: dangerous
• Gamma


  - 10⁻¹⁵ m

  - used in: medical tracers, cancer treatment

  - high dose: dangerous
• Opaque objects


  - do not transmit light

  - absorb some colours

  - reflect the colour of the object
• Transparent and translucent objects

  - some light passes through