The finest reading on the Vernier micrometer is

• A. 0.0001 in
• B. 0.001 in
• C. 0.01 in
• D. 0.0005 in

Answer: (A)

Vernier micrometers bring extra precision by using two scales: a main scale that shows measurements in thousandths of an inch and a Vernier scale that adds an additional reading of one-tenth of that increment. The line-up between the Vernier scale and the main scale pinpoints the extra amount to add, giving a smallest possible increment of 0.0001 inch. Therefore, the finest reading you can obtain with a standard Vernier micrometer is 0.0001 in. The other options are larger increments: 0.001 in is just the main scale step, 0.01 in is much larger, and 0.0005 in would not represent the Vernier’s standard least count.