In a murder investigation it was important to discover whether the victim was long sighted or short sighted. how could a detective decide by examining the spectacle s

See if the lenses in the glasses are concave or convex

Explanation:

A near sighted person would be wearing glasses with lenses that are concave in shape, so the edges of the glasses are thicker than their central section.

For a far sighted parson, the correction by the lenses have to be in the opposite, so the lenses are convex in shape, with the center of the lens thicker than the lenses' edges.

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