JEE Mains · Physics · STD 12 - Ray optics and optical instruments
- JEE Mains 2021
- Hard
- MCQ
Car \(B\) overtakes another car \(A\) at a relative speed of \(40\, ms^{-1}\). How fast will the image of car \({B}\) appear to move in the mirror of focal length \(10\, cm\) fitted in car \({A}\), when the car \({B}\) is \(1.9\, m\) away from the car \({A}\) ? (In \(ms^{-1}\))
Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) \(0.1\)
Step-by-step Solution
Detailed explanation
Mirror used is convex mirror (rear-view mirror)
\(\therefore \mathrm{V}_{\mathrm{I} / \mathrm{m}}=-\mathrm{m}^{2} \mathrm{~V}_{\mathrm{O} / \mathrm{m}}\)
Given,
\(\mathrm{V}_{\mathrm{O} / \mathrm{m}}=40 \mathrm{~m} / \mathrm{s}\)
\(\mathrm{m}=\frac{\mathrm{f}}{\mathrm{f}-\mathrm{u}}=\frac{10}{10+190}=\frac{10}{200}\)
\(\therefore \mathrm{V}_{\mathrm{L} / \mathrm{m}}=-\frac{1}{400} \times 40=-0.1 \mathrm{~m} / \mathrm{s}\)
\(\therefore\) Car will appear to move with speed \(0.1 \mathrm{~m} / \mathrm{s}\).
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