Waves 2

Waves 2

1. Reflection/Refraction

   • • Reflection Angle I = Angle R
   • • The light slows down because the block is dense.
     • The light speeds up and bends away from the normal as it enters a less dense medium
     • Refractive index n n1sin1 = n2sin2
     • h = c (speed of light) /v (speed through material)
     • n = sin1/sin2 = sin1/sinr
     • Sinc (critical angle) - 1/n

2. Lenses

   • Converging <--->
     • Objects greater than 2f from lens are diminished, inverted and real
     • Objects 2f from lens are magnified, inverted and real
     • Objects less then 1f from lens are magnified, upright and virtual
   • Diverging >---<
   • Power (D) = 1/f (cm)
     • Converging = + diverging = -
   • Power of a combination of lenses is found by adding (c) or subtracting (d)
     • p = 1/f = 1/u (object dist) + 1/v (image dist)
       • combining lenses p+ p+p / 1/f = 1/f + 1/f
   • magnification = Image height / object height
     • m = v/u

3. Huygens' Principle

   • Every point of a wave front is a new source of circular waves travelling forwards from that point, when you add all these movements and superposition together you get the position of a new wave source.
   • High frequency is diffracted little over a mountain, but low frequency is diffracted more
   • You can get interference patterns from 1 slit because the two wavelets act a two point sources, but the intensity drops off quickly
   • Interference patterns from two slits gives more even interference
   • nλ = dsinθ
     • n is the order of bright spots, λ is the wavelength of the light, d is the slit separation and θ is the angle between the bright spot and the source
   • d = 1/lines per m
   • d = 1000/lines per mm

4. Electro magnectic spectrum

   • Gamma, x-rays, ultra violet, light (400 - 700nm), infrared, microwaves, radiowaves
   • De Broglie wavelength = constant / momentum
   • λ = h/P(Planck's constant

5. Pulse Echo

   • Sound is refelcted to measure object distance
   • Unltra sound +20,000 Hz
   • Speed of sound = v = 2 distance(x) /t
     • Distance = x = vt/2
   • Resolution
     • Maximum detail that can be seen
   • Attenuation
     • Energy's lost as the wave travels though or is reflected off different surfaces
   • Ultra sound
     • The maximum depth of prenetration is approx 200x the wavelength
     • You can't see objects smaller than the wavelength
       • The higher the relolution the smaller the penetration
       • The lower the resolution the deeper the detail