Explain why a real image must be produced in a camera and how the object and the lens are positioned to produce a real image which is smaller than the object.

This is best explained through the use of an optics diagram, this is a little too complicated to explain in a short answer, and as I can't draw an appropriate diagram in this answer, I will point you to this excellent resource which explains what you have asked very well!

Go onto the BBC website (you should have access to it even if you aren't in the UK) and paste this after the BBC url,

/bitesize/intermediate2/physics/waves_and_optics/image_formation_from_lens/revision/1/