Understanding Polarization and Refraction of Electromagnetic Waves: A Review of Chapter 34, Study notes of Geology

Download Understanding Polarization and Refraction of Electromagnetic Waves: A Review of Chapter 34 and more Study notes Geology in PDF only on Docsity! November 12th Electromagnetic Waves Chapter 34 Review ! Waves are polarized if E field component of EM waves always points in same direction ! EM waves with randomly oriented E fields are unpolarized ! Intensity of unpolarized light after hitting a polarizing sheet ! Intensity of polarized light after hitting a polarizing sheet θ 2 0 cosII = 02 1 II = ! Law of reflection: Reflected ray lies in plane of incidence and angle for reflection is equal to angle of incidence ! Law of refraction: Refracted ray lies in plane of incidence and angle of refraction is related to angle of incidence by Snell’s law 11 θθ =′ 1122 sinsin θθ nn = Reflection & Refraction (Fig. 34-17) ! n is dimensionless constant called index of refraction ! Index of refraction, n for given medium is defined as ! Nothing has n <1, velocity of wave in medium is always less than the speed of light v cn == medium inlight of speed vacuuminlight of speed 1122 sinsin θθ nn = 2.42 1.33 Diamond Water 1.52Glass 1.00029Air Exactly 1Vacuum Index, nMedium Reflection & Refraction (Fig. 34-17) 12 nn = 12 θθ = 12 nn > 12 nn < 12 θθ < 12 θθ > 1122 sinsin θθ nn = Reflection & Refraction (Fig. 34-18) ! n for a medium is greater for shorter wavelengths (blue) than for longer (red) ! Blue light is bent more than red light Dispersion (Fig. 34-20) Dispersion (Fig. 34-20) ! Examples of chromatic dispersion ! White light through a prism ! Rainbow Dispersion (Figs. 34-21, 34-22) ! Reflected light is partially polarized ! When the light is incident at the Brewster angle its reflected light is fully polarized ⊥ to the plane of incident ! Refracted light is still unpolarized Polarization by reflection (Fig. 34-27) ! Found experimentally that reflected and refracted rays at the Brewster angle are ⊥ to each other ! From the general result ! We find the Brewster angle is 2211 sinsin θθ nn = BBB nnn θθθ cos)90sin(sin 221 =−= 1 21tan n n B −=θ 90=+ rB θθ Polarization by reflection (Fig. 34-27)