A gas absorbs 18 J of heat and work done on the gas is 12 J . Then, the change in internal energy of the gas

If the ratio of the absolute temperature of the sink and source of a Carnot engine is changed from $2: 3$ to $3: 4$, the efficiency of the engine change by

The ratio of the molar specific heat capacities of monoatomic and diatomic gases at constant pressure is

The frequency of fifth harmonic of a closed organ pipe is equal to the frequency of third harmonic of an open organ pipe. If the length of the open pipe is 72 cm , then length of the closed organ pipe is