Final answer:
Interference and diffraction patterns are the experimental evidence that indicate light is a wave.
Step-by-step explanation:
The experimental evidence that indicates light is a wave is interference and diffraction patterns.
Interference involves the superposition of two or more waves, resulting in the reinforcement or cancellation of certain points. When light passes through a double slit, it produces an interference pattern of bright and dark fringes, indicating that light behaves as a wave.
Diffraction is the bending and spreading of waves when they encounter an obstacle or pass through an aperture. Light exhibits diffraction when it passes through small openings, such as a narrow slit or the edges of an obstacle. This observation further confirms the wave nature of light.