Question

Which of the following clocks is more accurate?
A) Simple pendulum
B) Stop watch
C) Caesium clock
D) Hourglass

Answer 1

Hint: We know that atomic clocks are most accurate at this time and caesium clock is an atomic clock, its frequency is dependent on vibration on atoms. So, the caesium clock is more accurate than others.

Complete step by step solution:
We know that in simple pendulum a bob is oscillating and its frequency depicted the time but condition is that oscillation must be un damped, so, we created vacuum in it but, absolute zero pressure is not possible so, there is little damping in oscillations and inaccuracy in clock.
Stop watches are manually controlled so there are many possibilities of human made error.

A caesium atomic clock is a primary frequency standard in which electronic transitions between the two hyperfine ground states of caesium $133$ atoms are used to control the output frequency. Caesium clocks are the most accurate commercially produced time and frequency standards, and serve as the primary standard for the definition of the second in SI systems.

Hourglasses were an early dependable and accurate measure of time. The rate of flow of the sand is dependent on the depth in the upper reservoir, and the instrument will freeze in cold weather.

Note: In an atomic clock, the frequency of the quartz oscillator is transformed into a frequency that is applied to a collection of atoms. If the derived frequency is correct, it will cause many electrons in the atoms to change energy levels. In fact, the official measurement of the length of a second is determined by the frequency needed to make electrons jump between two specific energy levels in a caesium atom.