AIIMS2018Physics-Optics

AIIMS 2018 Physics Mirror Formula MCQ Question

Type: MCQ-conceptual-Medium-Class 12

A car is fitted with a convex side-view mirror of focal length 20 cm. A second car 2.8 m behind the first car is overtaking the first car at a relative speed of 15 m/s. The speed of the image of the second car as seen in the mirror of the first one is:

A

1/5 m/s

B

10 m/s

C

15 m/s

D

1/10 m/s

Correct Answer

Option A

Detailed Explanation

In this problem, we apply the mirror formula 1v+1u=1f\frac{1}{v} + \frac{1}{u} = \frac{1}{f} to derive the relationship between the rates of change of image distance vv and object distance uu. The derived equation dvdt=(fuf)dudt\frac{dv}{dt} = -\left(\frac{f}{u-f}\right) \frac{du}{dt} indicates that the rate of change of the image distance is directly proportional to the rate of change of the object distance, scaled by the factor (fuf)-\left(\frac{f}{u-f}\right). Given that dvdt=115 m/s\frac{dv}{dt} = \frac{1}{15} \text{ m/s}, option A correctly represents this relationship, while the other options are not applicable as they do not provide relevant information or values related to the derived equation. Understanding this relationship is crucial for analyzing how changes in object distance affect image distance in optics.

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