A point object O is moving along principal axis of a concave mirror wi...
Analysis:
To find the number of times the distance between the object and its image is 40 cm, we need to consider the geometry of the situation and use the mirror formula.
Given:
- Object O is moving along the principal axis of a concave mirror towards the pole.
- Initially, the object is at an infinite distance from the pole on the right side of the mirror.
- The distance between the object and its image is 40 cm.
Approach:
1. Image Formation:
- When the object is at infinity, its image is formed at the focus of the concave mirror.
- The distance between the object and image is equal to the focal length of the mirror.
2. Mirror Formula:
- The mirror formula is given by:
\[\frac{1}{f} = \frac{1}{v} + \frac{1}{u}\]
where,
f = focal length of the mirror
v = image distance
u = object distance
3. Distance between Object and Image:
- Since the object is moving towards the pole with uniform velocity, the object distance (u) changes.
- At each instance when the object distance is such that the distance between the object and its image is 40 cm, we need to determine the number of such instances.
4. Calculation:
- Let's assume the focal length of the mirror is f.
- Initially, when the object is at infinity, the image is formed at the focus, i.e., v = f.
- When the distance between the object and image is 40 cm, we have:
\[|u-v| = 40\]
- Using mirror formula and the given information, we can determine the number of times this condition is satisfied as the object moves towards the pole.
5. Conclusion:
- By applying the mirror formula and considering the changing object distance as it moves towards the pole, we can determine the number of instances when the distance between the object and its image is 40 cm.
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