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In parallax method for the determination of focal length of a concave mirror, the object should always be placed : (1) between the focus (F) and the centre of curvature (C) of the mirror ONLY (2) at any point beyond the focus (F) of the mirror (3) beyond the centre of curvature (C) of the mirror ONLY (4) between the pole (P) and the focus (F) of the concave mirror ONLY

1. between the focus (F) and the centre of curvature (C) of the mirror ONLY
2. at any point beyond the focus (F) of the mirror
3. beyond the centre of curvature (C) of the mirror ONLY
4. between the pole (P) and the focus (F) of the concave mirror ONLY

Correct answer: at any point beyond the focus (F) of the mirror

Solution

Placing the object at any point beyond the focus of the concave mirror ensures that a real and inverted image is formed, which is necessary for accurate measurement using the parallax method.

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