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JEE Main 2022 (28 Jul, Shift 2) · Reflection & Mirrors

Reflection & Mirrors question from JEE Main 2022 (28 Jul, Shift 2)

Q29JEE Main 2022 · 28 JUL · SHIFT 2Difficult

Reflection & Mirrors

An object 'O' is placed at a distance of 100 cm100\text{ cm} in front of a concave mirror of radius of curvature 200 cm200\text{ cm} as shown in the figure. The object starts moving towards the mirror at a speed 2 cm/s2\text{ cm/s}. The position of the image from the mirror after 10 s10\text{ s} will be at _________ cm\text{cm}.

Figure

Numerical answer type. Work it out, then open the answer.

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Answer: 400

  1. R=200 cm⇒f=−100 cmR = 200\text{ cm} \Rightarrow f = -100\text{ cm}. After 10 s the object has moved 20 cm: u=−80 cmu = -80\text{ cm}.
  2. 1v=1f−1u=−1100+180=1400\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = -\frac{1}{100} + \frac{1}{80} = \frac{1}{400}
  3. v=+400 cmv = +400\text{ cm} (virtual image behind the mirror)
  4. So the image is at 400 cm from the mirror.
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