A Window to the World of Negative Refraction

Images depicting the occurrence of a Snell's window in a swimming pool during an overcast day with the observer immersed in NIMs with the same refractive index (η = -1.33) and distinct relative magnetic permeabilities: μᵣ = -1 (top), μᵣ = -10 (middle) and μᵣ = -25 (bottom).