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This scenario describes a ray of light undergoing refraction at the interface between plastic and air. The ray in air travels parallel to the surface, which means the angle of refraction (r) in the air is 90° (this is the critical angle for the plastic-air interface).According to Snell's Law: n1 sin θ1 = n2 sin θ2Here, n1 = refractive index of plastic = 1.25θ1 = angle θ (angle of incidence in plastic)n2 = refractive index of air ≈ 1θ2 = angle of refraction in air = 90°So, 1.25 * sin θ = 1 * sin 90°1.25 * sin θ = 1 * 1sin θ = 1 / 1.25 = 0.8θ = sin-1(0.8) ≈ 53.13°The closest option is 53°.