Draw a neat and labelled diagram of a screw gauge. Name its main parts and state their functions.

Describe the procedure to measure the diameter of a wire with the help of a screw gauge.

A vernier has 10 divisions and they are equal to 9 divisions of main scale in length. If the main scale is calibrated in mm, what is its least count?

A microscope is provided with a main scale graduated with 20 divisions in 1cm and a vernier scale with 50 divisions on it of length same as of 49 divisions of main scale. Find the least count of the microscope.