Do you expect an echo to return to you more quickly on a hot day or a cold day? do you expect an echo to return to you more quickly on a hot day or a cold day? cold day. hot day. same on both days.

The answer is a cold day. This is because the air molecules are more compact during a cold day than a warm day. This because the low temperature makes the air molecules vibrate and collide at low energies. When sounds transmit through cold air, the distance between molecules is shorter than in warm air, hence  it takes less time for a molecule to 'bump' into its neighbor to transmit the sound energy.

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

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