A spectrometer gives the following reading when used to measure the angle of a prism.
Main scale reading : $58.5$ degree
Vernier scale reading : $09$ divisions
Given that $1$ division on main scale corresponds to $0 .5$ degree. Total divisions on the Vernier scale is $30$ and match with $29$ divisions of the main scale. The angle of the prism from the above data ....... $degree$
$59$
$58.59 $
$58.77$
$58.65$
$N$ divisions on the main scale of a vernier calliper coincide with $(N + 1 )$ divisions of the vernier scale. If each division of main scale is $a$ units , then the least count of the instrument is
In a screw gauge, $5$ complete rotations of the screw cause it to move a linear distance of $0.25\, cm$. There are $100$ circular scale divisions. The thickness of a wire measured by this screw gauge gives a reading of $4$ main scale divisions and $30$ circular scale divisions . Assuming negligible zero error, the thickness of the wire is