1. A lens measure is placed on a copper tube and is then rotated untill its legs are at right angles to the axis of the tube. The reading given by the instrument reads +10.50. What is the external diamter of the tube in mm, if the measure was calibrated for glass of refractive index 1.64.

not looking for the answer so to speak, more someone to explain the formulae i need to use and which ones to use, so i can figure it out myself.

2. A lens measure reads -0.25 when placed on a flat surface and +3.00 on the surface of a lens. If the measure was calibrated for n =1.523, what is the curvature of the surface?

Is this just 3.00 - 0.25 to get the actual power minus lens measure offset, and then put it into the radius of curvature formulae?

(1.523 - 1)1000

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2.75

? or am i doing something silly

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