Brewster's Angle, Laser

Even low-power laser pointers can cause permanent eye damage with direct or specular reflection exposure. Ensure the laser is tilted upward so all reflections (from prism and polarizing filter) pass over students' heads. Never aim the laser toward the audience. Use appropriate laser safety goggles during setup. Class 2 lasers (<1mW) are recommended for classroom use; Class 3A or 3B lasers require additional safety protocols.

The polarizing filter creates an additional reflection that cannot be easily shielded. Position the filter and laser so this reflection is directed safely away from students and below eye level. The black hood blocks beams from other prism faces, but remain vigilant about the primary reflected beam during prism rotation.

Purpose

A laser reflects off a glass prism through a polarizing filter. Rotating the prism sweeps the reflected beam across the screen; at Brewster's angle the reflected dot nearly vanishes, showing that p-polarized light is not reflected at $\theta_B = \arctan(n_2/n_1)$ .

Brewster's angle apparatus: polarizing filter on VWR lab jack, glass prism with black paper hood, green laser pointer clamped to ring stand, with two green laser dots visible on the wall behind

Slightly different angle of the same Brewster's angle setup, with a single green laser dot visible on the wall — the reflected beam is nearly extinguished

$Same apparatus from a wider angle showing both the reflected and refracted green laser dots separated on the wall$

Figure 1: Complete apparatus: green laser pointer on ring stand, glass prism with black paper hood on lab jack, and polarizing filter in bar clamp. Two green dots on the wall show the reflected and refracted beams.

Figure 2: Near Brewster's angle with the polarizer set for p-polarization: the reflected beam is nearly extinguished, leaving only one visible dot on the wall.

Figure 3: Away from Brewster's angle: both reflected and refracted beams are visible as separate green dots on the wall.

Glass Prism

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Prism Hood

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Danger: Laser Safety - Eye Hazard

Warning: Reflected Beam Control

Purpose

Safety Warnings

Danger: Laser Safety - Eye Hazard

Warning: Reflected Beam Control

Purpose