Final answer:
The distance between the inner cone and the metal ideally should be 25 cm behind the lens.
Step-by-step explanation:
The distance between the inner cone and the metal ideally should be 25 cm behind the lens.
When a concave mirror is used to project an image, the object distance is located at the focal length of the mirror. In this case, the focal length is given as 25 cm, so the object distance would also be 25 cm behind the lens.
This positioning allows for a clear and focused image to be formed.