Question

A spherometer has 250 equal divisions marked along the periphery of its disc and one full rotation of the disc advances on the main scale by 0.0625 cm. The least count of the spherometer is

• A. 2.5 × 10⁻² cm.
• B. 25 × 10⁻³ cm
• C. 2.5 × 10⁻⁴ cm
• D. None of the above.

Answer 1

Answer: (C)

2.5 × 10⁻⁴ cm

Answer 2

v = $\frac { 4 } { 3 }$ πr³

∴ ∆V/V = 3(∆r/r) = 3 × 1% = 3%

Hence (3) is correct.