Test Index

WAEC Physics 2012 Paper

Question : 26

Total: 47

A ray of light passes from air to water to glass to air. Given that the refractive index for light passing from air to water is

\;\frac{4}{3}

and air to glass is

\;\frac{3}{2}

, calculate the refractive index of glass relative to water

0.50
0.67
0.75
1.13

Validate

Solution:

Concept:

When both refractive indices are given from air, divide the index for glass by the index for water to find the refractive index of glass relative to water.

Explanation:

Let

{}_a\eta_w = \frac{4}{3}

and

{}_a\eta_g = \frac{3}{2}

The refractive index of glass relative to water is:

{}_w\eta_g = \frac{{}_a\eta_g}{{}_a\eta_w}

Substitute the given values:

{}_w\eta_g = \frac{\frac{3}{2}}{\frac{4}{3}} = \frac{3}{2} \times \frac{3}{4} = \frac{9}{8}

\frac{9}{8} = 1.125

, which is approximately

1.13

Answer:

D. 1.13

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