Question.
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 ?
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 device with minimum count is the most suitable to measure length.
(a) Least count of vernier callipers
$=1$ standard division $(S D)-1$ vernier division $(V D)$
$=1-\frac{9}{10}=\frac{1}{10}=0.01 \mathrm{~cm}$
(b) Least count of screw gauge $=\frac{\text { Pitch }}{\text { Number of divisions }}$
$=\frac{1}{1000}=0.001 \mathrm{~cm}$
(c) Least count of an optical device $=$ Wavelength of light $\sim 10^{-5} \mathrm{~cm}$
$=0.00001 \mathrm{~cm}$
Hence, it can be inferred that an optical instrument is the most suitable device to measure length.
A device with minimum count is the most suitable to measure length.
(a) Least count of vernier callipers
$=1$ standard division $(S D)-1$ vernier division $(V D)$
$=1-\frac{9}{10}=\frac{1}{10}=0.01 \mathrm{~cm}$
(b) Least count of screw gauge $=\frac{\text { Pitch }}{\text { Number of divisions }}$
$=\frac{1}{1000}=0.001 \mathrm{~cm}$
(c) Least count of an optical device $=$ Wavelength of light $\sim 10^{-5} \mathrm{~cm}$
$=0.00001 \mathrm{~cm}$
Hence, it can be inferred that an optical instrument is the most suitable device to measure length.
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.