Question

Which of the following instruments is not used for the measurement of length?
A) Atomic clock
B) Vernier callipers
C) Screw gauge
D) Spherometer

Answer 1

Length is the measurement of distance from end to end. The standard measurement of length is meter (m). The other units of length are kilometer, centimeter, millimeter etc. It is useful in identifying the size of an object or calculating the distance between two points.

Complete step by step solution:
Measurement of length is the process of measuring the distance between two points in terms of width, depth, thickness and height. The various instrument used in measurement of length are:

Vernier Callipers: it is an instrument used for making linear measurements very precisely, it was introduced by Pierre Vernier of France in 1631. The measurement readings of vernier callipers are in centimetres (cm) and it is precise up to 2 decimal places.

Screw gauge: the width of a sheet of metal or diameter of a thin wire can be measured with the help of a screw gauge. The construction is as follows: a U-shaped mount is fixed with a screwed pin and which is fixed to a thimble. A scale in mm is inscribed side by side to the thimble axis. With the U shaped metallic mount, a screw gauge can accurately measure even the tiniest length.

Spherometer : A spherometer is an instrument used for precise measurement of the diameter or radius of curvature of a curved surface. It works on the principle of the micrometer screw and has a metallic triangular frame supported on three legs. The tips of the three legs form an equilateral triangle and lie on the radius.

An Atomic clock is a special device that is designed to measure the precise length of seconds and uses the resonance frequencies of atoms as its resonator. The International System of Units (SI) defines the second as the time it takes a caesium-133 atom in a precisely defined state to oscillate exactly.

Therefore all the options are used in measuring length or width of different kinds of objects whereas option (A) is used for precise timekeeping devices.

Note: The above instruments are the common length measuring instrument in the lab or practical work. Some traditional length measuring methods are hand, ruler, rope, arm length etc.