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Image of an object approaching a convex mirror of radius of curvature 20 ~m along its optical axis is observed to move from 25 3 ~m to 50 7 ~m in 30 ~s . What is the speed of the object in km h ⁻¹ ?

Correct answer

3

Step-by-step solution

Using mirror formula twice, 1 +25 / 3 + 1 -u₁ = 1 +10 or 1 u₁ = 3 25 - 1 10 or u₁=50 ~m and, 1 (+50 / 7) + 1 -u₂ = 1 +10 1 u₂ = 7 50 - 1 10 or u₂=25 ~m Speed of object = u₁-u₂ time = 25 30 ~ms ⁻¹=3 kmh ⁻¹ The answer is 3 .

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