1)

A student measured the length of a rod and wrote it as 3.50 cm. Which instrument did he use to measure it?

A) A meter scale

B) Avernier calliper where the 10 divisions in vernier scale matches with 9 divisions in main scale and main scale has 10 divisions in 1 cm.

C) A screw gauge having 100 divisions in the circular scale and pitch as 1 mm.

D) A screw gauge having 50 divisions in the circular scale and pitch as 1 mm

**Answer:**

Option B**Explanation:**

If student measures 3.50 cm. it means that there is an uncertanily of order 0.01cm. For vernier scale with 1MSD=1mm

and 9MSD=10VSD

LC of vernier caliper =1 MSD-1VSD

= $\frac{1}{10}\left(1-\frac{9}{10}\right)$

= $\frac{1}{100}$ cm