List of top Physics Questions on Ideal Gases asked in IIT JAM PH

An ideal blackbody at temperature \( T \), emits radiation of energy density \( u \). The corresponding value for a material at temperature \( \frac{T}{2} \) is \( \frac{u}{256} \). Its emissivity is ............... (Round off to three decimal places).
Consider \( N_i \) number of ideal gas particles enclosed in a volume \( V_1 \). If the volume is changed to \( V_2 \) and the number of particles is reduced by half, the mean free path becomes four times of its initial value. The ratio \( \frac{V_1}{V_2} \) is ........... (Round off to one decimal place).