Question

Assertion – the basic of Laplace correction was that exchange of heat between the region of compression and rarefaction in air is not possible.
Reason: Air is a bad conductor of heat and velocity of sound in air is large.

A.) If both assertion and reason are true and reason is the correct explanation of assertion.
B.) If both assertion and reason are true but reason is not the correct explanation of assertion.
C.) If assertion is correct but reason is not correct
D.) If assertion and reason both are incorrect.

Answer 1

Hint: Study the Laplace correction to the Newtonian formula which gives the velocity of sound in air. Study about the isothermal and adiabatic processes and try to see if the assertion and the reason individually and then think if they have any relation or not.

Complete step by step answer:
Laplace correction is a correction to the calculation of velocity of sound in a gas.

In the Newtonian formula for speed of propagation of sound he assumed that the process is isothermal. Newton assumed that the pressure and volume changes that occur when a sound wave travels through a gas is an isothermal process. So according to him, the temperature remains constant throughout the process.

Laplace made a correction to this assumption. Laplace corrected the Newtonian formula by assuming that the compression and rarefaction takes place very fast, so no heat will be exchanged during the process. So, the temperature does not remain constant as assumed by Newton and the process is an adiabatic process.

The air is a bad conductor of heat and it will not allow heat to be exchanged in the region of compression and rarefaction.

So, the assertion is true and the reason is also true. But the reason is not the correct explanation of the assertion.

The correct option is (B)

Note: In an isothermal process is a thermodynamic process where the temperature of the system remains constant. In an adiabatic process, there is no heat will be exchanged between the system and surrounding during the process.