Which of the following is the most precise device for measuring length : a vernier calipers 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 ?
a vernier calipers 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 ?
Solution and Explanation
A device with minimum count is the most suitable to measure length.
Least count of vernier calipers
= 1 standard division (SD) - 1 vernier division (VD)
= 1 - \(\frac{9}{10}\) = \(\frac{1}{10}\) = 0.01 cm
Least count of screw gauge = \(\frac{\text{Pitch}}{\text{Number of divisions}}\)
= \(\frac{1}{1000}\) = 0.001 cm
Least count of an optical device = Wavelength of light \(\sim\) \(10^{-5}\) cm = 0.00001 cm
Hence, it can be inferred that an optical instrument is the most suitable device to measure length.
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Concepts Used:
Units and Measurement
Unit:
A unit of a physical quantity is an arbitrarily chosen standard that is broadly acknowledged by the society and in terms of which other quantities of similar nature may be measured.
Measurement:
The process of measurement is basically a comparison process. To measure a physical quantity, we have to find out how many times a standard amount of that physical quantity is present in the quantity being measured. The number thus obtained is known as the magnitude and the standard chosen is called the unit of the physical quantity.
Read More: Fundamental and Derived Units of Measurement
System of Units:
- CGS system
- FPS system
- MKS system
- SI units
Types of Units:
Fundamental Units -
The units defined for the fundamental quantities are called fundamental units.
Derived Units -
The units of all other physical quantities which are derived from the fundamental units are called the derived units.