Answer the following about sound.

Thapelo uses the set-up below to produce sound. He pushes the metal plate down at point X and then releases it. When the metal plate is released, it vibrates and produces sound.

1. aDescribe how sound travels through air. [1]
2. bWhat changes can be made to the set-up to produce sound of a higher pitch? [1]
3. cWhat is the relationship between the frequency of vibrations and the pitch of sound? [1]
4. dA boy placed his foot on the metal bar of a railway track and felt vibrations from an oncoming train out of view, though he could not hear it. Explain this in terms of particle arrangement. [2]

You'll mark your own answer against the marking guide when you hand it in.