How will you demonstrate that water vapour is present in air?

The presence of water vapour in the air can be demonstrated by the following experiment:

We take a steel tumbler and put some well-crushed ice in it. Allow the steel tumbler to stand undisturbed for about 5 minutes with the ice in it. We would observe that a large number of tiny drops of water appear on the outer surface of the steel tumbler. This happens because the air around the steel tumbler contains water vapour. When these water vapours come in contact with the cold, outside surface of the steel tumbler, they condense to form tiny droplets of water.