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# In an experiment the angles are measured using an instrument where $29$ divisions of main scale exactly coincide with $30$ division of vernier scale.If the smallest division in main scale is half a degree, then the least count of the instrument is

(a)half minute (b)one degree (c)half degree (d)one minute

vernier scale division$=\large\frac{29}{30}$ main scale division
least count$=1 MSD-1VSD$
$\qquad\qquad=1 MSD-\large\frac{29}{30}$$MSD \qquad\qquad=\large\frac{1}{30}$$ MSD=\large\frac{1}{30}$$\times .5 degree$
$\qquad\qquad=1 \;minute$
Hence d is the correct answer.

edited Jan 9, 2014 by meena.p