When temperature of the atmosphere rises, air …………… .

1. Contracts
2. Compresses
3. Expands
4. Dissipates

Air containing water vapour is …………… than dry air.

1. Denser
2. Lighter
3. Heavier
4. Thinner

The lowermost limit of this layer is tropopause

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere

The atmospheric layer which reflects the low frequency radio waves but absorbs the medium and high frequency waves

1. Exosphere
2. Ionosphere
3. Thermosphere
4. Mesosphere