Question 4

**Analysing the scales** From Fig. 1 (zero setting): the main scale has 10 divisions per cm, so 1 MSD = 0.1 cm. The Vernier scale has 10 divisions and its total length spans exactly 7 main-scale divisions (its 10th mark coincides with the 0.7 cm mark). Hence 1 VSD = 0.7/10 = 0.07 cm, Least count = 1 MSD − 1 VSD = 0.10 − 0.07 = 0.03 cm. There is no zero error since the zeros coincide in Fig. 1. **Reading Fig. 2** - The Vernier zero lies just past the 0.1 cm main-scale mark → main scale reading = 0.1 cm. - The 1st Vernier division coincides with the 0.2 cm main-scale mark → coinciding division n = 1. D = MSR + n × LC = 0.1 + 1 × 0.03 = 0.13 cm (Check: Vernier zero at 0.13 cm, 1st Vernier mark at 0.13 + 0.07 = 0.20 cm, matching the 2nd main-scale mark, consistent with the figure.)

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