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:1. A vernier caliper with 20 divisions on the sliding scale2. A screw gauge of pitch 1 mm and 100 divisions on the circular scale3. An optical instrument that can measure length to within a wavelength of light?
Answer» 1. Least measurement possible with vernier callipers = 1/20 mm = 5 × 10^-5 m 2. Least measurement possible with screw gauge = 1/100 mm = 1 × 10^-5 m 3. Least measurement possible with the optical instrument = 300 nm = 3 × 10^-7 m Clearly (c) is the most precise device.

Which of the following is the most precise device for measuring length:1. A vernier caliper with 20 divisions on the sliding scale2. A screw gauge of pitch 1 mm and 100 divisions on the circular scale3. An optical instrument that can measure length to within a wavelength of light?

Answer»

1. Least measurement possible with vernier callipers

= 1/20 mm = 5 × 10^-5 m

2. Least measurement possible with screw gauge

= 1/100 mm = 1 × 10^-5 m

3. Least measurement possible with the optical instrument

= 300 nm = 3 × 10^-7 m

Clearly (c) is the most precise device.