waves_05 - waves_05 ELECTROMAGNETIC WAVES 1 waves_05...

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Unformatted text preview: waves_05 ELECTROMAGNETIC WAVES 1 waves_05: MINDMAP SUMMARY - ELECTROMAGNETIC WAVES Electromagnetic waves, electromagnetic radiation, speed of light, electromagnetic spectrum, electric field, magnetic field, reflection, refraction, refractive index, Snell’s Law, superposition principle, constructive interference, destructive interference, thin film interference, conditions for constructive & destructive interferecne, path length difference, phase difference, phase changes upon reflection, wave – particle models, photons, E = hf , energy [ J and eV], absorption and emission of light, ground state, excited states 2 c = 3.0 × 10 8 m.s-1 c n v 1 1 2 2 sin sin n n o f f n f 2 1 2 1 f o 2 2 2 2 d d n c f E h f • Transverse wave • Oscillating quantities: electric and magnetic fields , in phase, perpendicular to each other and direction of propagation • Can travel through vacuum, speed is c = 3.0 x 10 8 m.s-1 • In transparent medium, speed is v = c / n where n is a property of the medium called refractive index • When electromagnetic waves are emitted or absorbed by an atom, done so in quanta of energy: E = h f CP 551 3 ELECTROMAGNETIC WAVES Electromagnetic Spectrum Gamma rays X-rays Ultraviolet Visible Infrared Microwaves Radio Increasing frequency Increasing wavelength c = f E = h f CP 588 4 31 32 33 34 35 36 visible REFRACTION How can we see? What produces an image in an optical microscope? What happens when light passes through a transparent material? dispersion CP 588 5 c n v 1 1 2 2 sin sin n n The ratio of the speed of an electromagnetic wave, c in vacuum to that in the medium, v is defined as the refractive index , n When a wave enters a new medium (different wave speed) at an angle the wavefront must bend. This bending is called refraction. The amount of bending is described by Snell's Law (Law of Refaction) CP 588 6 1 2 2 1 n 2 n 1 normal n 1 < n 2 1 1 2 2 sin sin n n CP 588 7 normal normal n 1 n 1 n 2 n 2 n 1 < n 2 sin 1 > sin 2 refracted ray bent towards normal n 1 > n 2 sin 1 < sin 2 refracted ray bent away from normal Critical angle sin 2 = 1 sin 1 = sin C = n 2 / n 1 1 1 2 2 CP 588 1 1 2 2 sin sin n n reflection reflection total internal reflection 8 9 1 2 medium 1 medium 2 1 2 1 2 1 2 1 2 1 2 n n v v f f Plane wave incident upon an interface I x + X 1 1 sin 2 2 x t y A T 2 1 2 sin 2 2 I I I x x x t if x x y A T 10 1 2 medium 1 medium 2 1 2 1 2 1 2 1 2 1 2 n n v v f f Plane wave incident upon an interface 1 1 2 2 sin sin n n Snell’s Law 1 2 normal Refraction...
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waves_05 - waves_05 ELECTROMAGNETIC WAVES 1 waves_05...

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