How can you experimentally determine the focal length of a concave mirror?

Correct option is C

Correct Answer: C) Measure the distance between the mirror and the image of a distant object formed by it.

Explanation:
To experimentally determine the focal length of a concave mirror, follow this method:

1. Place the concave mirror facing a distant object (e.g., the Sun or a building far away).
2. Adjust a screen (like a piece of paper) until a sharp, focused image of the distant object is formed on the screen.
3. The distance between the mirror and the screen is equal to the focal length (f) of the concave mirror.

This method works because the rays from a distant object are nearly parallel when they strike the mirror. These parallel rays converge at the focal point, and the distance from the focal point to the mirror is the focal length.

Information Booster:

• Focal Length (f): The distance between the pole (P) of the mirror and its focus (F).
  
• Centre of Curvature (C): The focal length is related to the radius of curvature (R) by f=R/2.
  
• Mirror Formula: The relationship between object distance (uuu), image distance (v), and focal length is:

$$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$$​​

• Practical Uses of Concave Mirrors: Found in telescopes, headlights, shaving mirrors, and solar cookers.
• Experiment Precautions: Ensure the object is very distant, and use a dark room or a shaded area to easily observe the image.