Final Design

Your final design needs to be :-

A 3D rendered drawing showing the materials the lamp would be made from. Light and shadow will be key to showing the 3D qualities of your drawing. You can choose the media that this drawing will be produced in.
A 2D drawing that shows the inside of your design and how it is put together - a cut away view / cross sectional view.
An exploded view shows all the parts and how they relate to each other.
A model of the final design to scale ( 1:2, 1:3, 1:4)

3D Rendered Drawing

Your 3D rendered final drawing could be drawn in ISOMETRIC or PERSPECTIVE ...

Your final 3D drawing needs to be rendered so that it looks like the material that you want your design to be made from.

You can use what ever medias you like to produce the rendered effect.

Using Different Media

Product Design Rendering

Cross sectional views of your design will show how the product is put together and where all the parts go and how it works.

Another way to explain your design is to show exploded views of your design or some parts of your design.