Which of the following is the most precise device for measuring length

1.	Which of the following is the most precise device for measuring length: a vernier callipers with 20 divisions on the sliding scale a screw gauge of pitch 1 mm and 100 divisions on the circular scale an optical instrument that can measure length to within a wavelength of light?
Answer» A device with minimum count is the most suitable to measure length. Least count of vernier callipers = 1 standard division (SD) – 1 vernier division (VD) 1 - 9/10 = 1/10 = 0.01 cm Least count of screw gauge = Pitch/Number of division = 1/1000 = 0.001 cm Least count of an optical device = Wavelength of light ∼ 10^–5 cm = 0.00001 cm Hence, it can be inferred that an optical instrument is the most suitable device to measure length.

Which of the following is the most precise device for measuring length: a vernier callipers with 20 divisions on the sliding scale a screw gauge of pitch 1 mm and 100 divisions on the circular scale an optical instrument that can measure length to within a wavelength of light?

Answer»

A device with minimum count is the most suitable to measure length.

Least count of vernier callipers

= 1 standard division (SD) – 1 vernier division (VD)

1 - 9/10 = 1/10 = 0.01 cm

Least count of screw gauge =

Pitch/Number of division = 1/1000 = 0.001 cm

Least count of an optical device = Wavelength of light ∼ 10^–5 cm

= 0.00001 cm

Hence, it can be inferred that an optical instrument is the most suitable device to measure length.