Practice portal › Experimental Skills › Vernier Callipers
Asked in JEE Main 27th Jan 1st Shift 2024 · Least count
Idea: a spherometer reads a small vertical distance with a fine screw, so it measures thickness and curvature, both of which are lengths.
Thickness of a thin plate: read directly as the screw's travel. Measurable.
Radius of curvature, concave or convex: from the sagitta h and the leg spacing l, R=(l²)/(6h)+h/2. Measurable.
Specific rotation of a liquid is the angle through which the liquid turns the plane of polarisation, per unit concentration and path length. That is an optical rotation, measured with a polarimeter, and no length measurement gives it.
So (b) is the quantity a spherometer cannot measure.
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