JAMB Physics 2012 Paper

Concept:Refraction makes an object viewed through a glass block appear closer to the observer than its actual distance.Explanation:The real thickness of the glass block is $t = 10\ \text{cm}$.The refractive index of glass is $\mu = 1.5$.The apparent depth is calculated as:$$\text{apparent depth} = \frac{\text{real thickness}}{\mu} = \frac{10}{1.5} = 6.67\ \text{cm}$$The displacement of the object is the difference between the real thickness and the apparent depth:$$\text{displacement} = 10 - 6.67 = 3.33\ \text{cm}$$Answer:A. 3.33 cm