sphero meter expriment

 take a spherometer and find its least count generally it is o.oo1cm.Place it on the convex surface of the mirror placed on the glass slab.Rotate the screw until all the three legs balance on the convex surface observe the pitch scale reading(PSR) generally zero and the circular scale reading(CSR) and obtain the total reading by adding the PSR and the product of least count and CSR .then substitute this value divided by 2 in the radius of curvature formula.