PHYS1220 Lecture 14: PHYS1220 Week 7.14
10 Oct 2018
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Document Summary
An interference effect is seen in the reflection of light from water with oil on top: rainbow coloured fringes are visible. From a lower to higher refractive index, light undergoes a. 180 phase change: higher to lower has no phase change. If the distance that the light needs to travel within the oil is equal to an order of , there will be constructive/destructive interference. Ray reflected in glass at point b has no phase change. Ray reflected at c has experienced a phase change and may interfere with the light reflected at b. Creates concentric rings: when viewed in reflections, the centre is dark due to half phase changes, when viewed in transmissions, the centre is bright due to half phase changes. Can be used to determine how flat a surface is. Fringes can be easily generated by placing a thin wire/sheet along one edge of the object and illuminating with a monochromatic light.
