A thin layer of oil ( ) floats on water ( )

PHYSICS · Single correct · A Level · Physics · Waves · Waves

Problem

A thin layer of oil (n=1.45n=1.45) floats on water (n=1.33n=1.33). Monochromatic light in air is incident normally on the oil. Which combination of phase changes occurs for the two rays that interfere after reflecting from the top and bottom surfaces of the oil layer? (a) 0∘0^\circ for the reflection at the air–oil surface and 180∘180^\circ for the reflection at the oil–water surface (b) 0∘0^\circ for both reflections (c) 180∘180^\circ for the reflection at the air–oil surface and 0∘0^\circ for the reflection at the oil–water surface (d) 180∘180^\circ for both reflections

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