NCERT Exercise 1.6 - Units and Measurements
Question: Which of the following is the most precise device for measuring length: (a) a vernier callipers with 20 divisions on the sliding scale coinciding with 19 main scale divisions (b) a screw gauge of pitch 1 mm and 100 divisions on the circular scale (c) an optical instrument that can measure length to within a wavelength of light?
Answer: **(c) An optical instrument** is the most precise device.
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