How does the speed of sound change with change in (i) amplitude and (ii) wavelength, of sound wave?

In which medium the speed of sound is more — humid air or dry air? Give a reason to your answer.

Describe a simple experiment which demonstrates that the sound produced by a tuning fork is due to vibration of it's arms.

Describe in brief, with the aid of a labelled diagram, an experiment to demonstrate that a material medium is necessary for the propagation of sound.