The correct option is Between the pole and the principal focus.
Explanation
A concave mirror is a converging mirror that generally forms real and inverted images when the object is placed outside its principal focus. The nature, size, and position of the image depend on the distance of the object from the mirror's pole relative to the focal length and radius of curvature.
Position-wise Analysis
- Between the pole and the principal focus (Option a): When an object is placed within the focal length (between the Pole and Focus), the reflected rays diverge. When extended backward, they appear to meet behind the mirror. Consequently, the image formed is virtual, erect, and magnified. This property is utilized in shaving mirrors and dentist mirrors. (Correct)
- At the centre of curvature (Option b): Placing the object at the centre of curvature results in a real, inverted image of the same size as the object, formed at the centre of curvature itself. (Incorrect)
- Between the focus and the centre of curvature (Option c): In this position, the image formed is real, inverted, and magnified. It is located beyond the centre of curvature. (Incorrect)
- Beyond the centre of curvature (Option d): When the object is placed beyond the centre of curvature, the image formed is real, inverted, and diminished. It is located between the principal focus and the centre of curvature. (Incorrect)
Key Takeaway: A concave mirror produces a virtual and erect image only when the object is placed between the pole and the principal focus. For all other object positions, the image is real and inverted.