Lab 12 - Wave Diffraction Introduction This hands-on lab activity explores the phenomenon of constructive and destructive interference for light waves. Constructive and destructive interference involves the superposition of waves (e.g., waves on a vibrating string or sound waves emerging from two or more speakers). The basic principle of superposition states that when two waves overlap, the actual displacement of any point on the resultant wave is found by the vector addition of the two displacements. This principle applies to both sinusoidal waves and wave pulses. Superposition also applies to both longitudinal and transverse waves. Superposition applies to light waves as well. This laboratory activity looks at light passing through small slits also known as diffraction gratings. The constructive and destructive interference patterns can be used to experimentally determine the wavelengths of the incident light. Materials From Lab Kit: Laser Pointer Diffraction grating Student Provided: Ruler or meter stick