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Fresnel’s equations – Theory of reflection

LEP 2.5.03

Related topics Electromagnetic theory of light, reflection coefficient, reflection factor, Brewster’s law, law of refraction, polarization, polarization level. Principle and task Plane-polarized light is reflected at a glas surface. Both the rotation of the plane of polarization and the intensity of the reflected light are to be determined and compared with Frewsnel’s formulae for reflection. Equipment Laser, He-Ne 1.0 mW, 220 V AC Polarising filter, on stem Prism, 60 degrees, h 36.4 mm, flint Prism table with holder Photoelement f. opt. base plt. Protractor scale with pointer Articulated radial holder Stand tube Tripod base -PASSH-base -PASSRight angle clamp -PASSSupport rod …ver más…

2. The laser is set up again in the normal position for the determination of the degree of rotation of the polarization plane by reflection. The photocell is lined up to the direction of the beam without the prism in place. Using a polarization filter mounted in front of the laser for a precise determination of the plane of oscillation, the filter is turned until the registered intensity is at a minimum. Then the filter is turned through 45 ° and the prism placed in position using the familiar method. The degree of rotation of the plane of polarization for the reflected beam is found with a second polarization filter located between the prism and the detector. The angle of incidence is changed in 5 ° steps. The angle of rotation for the plane of polarization is the average of a number of measurements.

Theory and evaluation In a light wave the electrical field vector E and the magnetic vector B oscillate perpendicular to one another and in phase. Their magnitudes are governed by Maxwell’s equation: |B| = n |E| Fig. 2: Articulated radial holder with prism arrangement for finding the reflection at = 0 ° (1 darkened side of prism, 2 prism table, 3 protractor scale, 4 pointer, 5 support rod, 6 light beam). (1)

where n is the refractive index of the medium through which the light passes. The transported wave engergy in the direction of propagation is represented by the Poynting vector. The