A transparent plate is 6.0 cm thick and consists of two equal layers

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

Problem

A transparent plate is 6.0 cm thick and consists of two equal layers. The upper layer has an absolute refractive index of 1.50, while in the lower layer the speed of light is 2.25×108 m s−12.25\times10^{8}\,\text{m s}^{-1}. How much total time does a light ray take to emerge from the opposite face after entering normally at the top surface? (Take c=3.0×108 m s−1c = 3.0\times10^{8}\,\text{m s}^{-1}.) (a) 0.20 ns0.20\,\text{ns} (b) 0.28 ns0.28\,\text{ns} (c) 0.15 ns0.15\,\text{ns} (d) 0.30 ns0.30\,\text{ns}

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