Brewster's Angle - Physics Demonstrations - Brewster's Angle | Physics Undergraduate Labs

Purpose

Light reflecting from a glass plate at Brewster's angle ( $\theta_B \approx 56°$ for glass) is completely linearly polarized. Two crossed polarizing filters placed in the reflected beam demonstrate this: one blocks the reflected light while the other transmits it. Rotating each filter 90° reverses the effect.

Glass plate supported between wooden blocks on a bench, illuminated by a flashlight mounted in a finger clamp on a ring stand; two polarizing filters lean against lead bricks behind the glass plate

Side view of the same setup showing the glass plate between blocks, two polarizing filters standing behind it, and the flashlight on the ring stand above casting light down onto the glass

Multiple glass plates of different sizes arranged on the bench with the ring stand clamp visible, showing available apparatus

Figure 1: Setup: glass plate between wooden blocks, flashlight in finger clamp on ring stand, and crossed polarizing filters leaning against lead bricks. One filter blocks the reflected light, the other transmits it.

Figure 2: Side view showing the flashlight angle and polarizing filters. Rotating each filter 90° reverses which one blocks and which transmits the reflected beam.

Figure 3: Multiple glass plates of different sizes available for the demonstration.

Mini Maglite (LED)

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