Which of the following is the most precise device for measuring length:
(a) a vernier callipers with 20 divisions on the sliding scale
(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 ?
Solution:
(a)Least count of vernier calipers = 1 /20 = 0.05 cm
(b) Least count of screw gauge =1/100 = 0.01 cm
(c) Least count of an optical device =1/ 105 = 0.00001 cm
( Wavelength of light =10–5 cm)
Optical instrument has least count, Hence it is the most precise device for measuring length.
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