If a bell is placed in a jar and the air in the jar is replaced with a gas of a higher density, what is the effect on the speed of sound when the bell is rung?

The correct answer is that the sound travels faster when the density of the gas in the jar is increased, which might seem counterintuitive at first. The speed of sound in a medium is determined by a combination of factors, including the medium's density and elasticity. While increasing density can slow down sound as it increases inertia, in gases, the effect of temperature and elasticity plays a more significant role.

In this case, when the gas density increases, the molecule count in the same volume also increases, allowing for more efficient transmission of sound waves. The speed of sound is proportional to the square root of the ratio of the medium's bulk modulus (a measure of elasticity) to its density. If the gas's bulk modulus is significantly high, as is the case with many gases at higher densities, the resultant speed can indeed increase.

This effect can be contrasted with what happens in solids and liquids, where density has a more straightforward effect on sound speed. By understanding the interplay between the medium's density and elasticity, it's clear why the speed of sound increases in this scenario.