Embibe Experts Solutions for Chapter: Kinetic Theory of Gases and Radiation, Exercise 1: Exercise 1

Assertion: The root mean square velocity of molecules of a gas having Maxwellian distribution of velocities is higher than their most probable velocity at any temperature.

Reason: A very small number of molecules of a gas possessing very large velocities increases the root mean square velocity without affecting the most probable velocity.

An ideal gas is enclosed in a cylinder at pressure of $2 \mathrm{atm}$ and temperature, $300 \mathrm{K}$. Then mean time between two successive collisions is $6\times {10}^{-8} \mathrm{s}$. If the pressure is doubled and temperature is increased to $500 \mathrm{K}$, the mean time between two successive collisions will be close to

According to Kirchhoff's law-

The temperature of bodies $X$ and $Y$ vary with time as shown in the figure. If emissivity of bodies $X$ and $Y$ are $e_x$ and $e_y$ and absorptive powers are $A_x$ and $A_y$, (assume other conditions are identical for both), then

Assertion: Absorptive power is a dimensionless quantity and a body having low emissive power should have low absorptive power.

Reason: The ratio of emissive power to absorptive power is same for all bodies at a given temperature and is equal to the emissive power of a black body at that temperature.

If the absorption coefficient and reflection coefficient of a surface of a body are $0.4$ and $0.6$ respectively then

Assertion: A body that is a good radiator is also a good absorber of radiation at a given wavelength.

Reason: According to Kirchhoff's law the absorptivity of a body is equal to its emissivity at a given wavelength.

Which of the following is extensive variable?