Laser and Mirror - Physics Demonstrations - Laser and Mirror | Physics Undergraduate Labs

This demonstration uses a Class IIIa laser (typically 1-5 mW). Direct eye exposure can cause temporary flash blindness and afterimages. Never aim the laser toward audience seating areas. Test all beam paths before students enter. Use protective eyewear for anyone within 3 meters of the setup. Secure the laser mount to prevent accidental redirection during the demonstration.

Purpose

A green laser aimed at a flat mirror demonstrates the law of reflection ( $\theta_i = \theta_r$ ). Fog or chalk dust makes the incident and reflected beam paths visible, giving students direct visual confirmation that the angle of incidence equals the angle of reflection.

Green laser pointer mounted in a clamp on a blue stand, aimed at a flat mirror lying on the table; green incident and reflected beams form an X pattern on the mirror surface; fog machine with red button visible behind the mirror

Figure 1: The demonstration setup shows the laser mounted at approximately 45 degrees to the mirror surface. The fog makes both incident and reflected beams visible, clearly illustrating the symmetric angles predicted by the law of reflection.

Portrait-Sized Mirror

1

Safety Warnings

Warning: Class IIIa Laser Hazard

Purpose