Q159 / 180 · KCET 2019 · Physics
A Point object is moving uniformly towards the pole of a concave mirror of focal length \( 25 \mathrm{~cm} \)
along its axis as shown below. The speed of the object is \( 1 \mathrm{~ms}^{-1} \). At \( \mathrm{t}=0 \), the distance of the
object from the mirror is \( 50 \mathrm{~cm} \). The average velocity of theimage formed by the mirror
between time \( t=0 \) and \( t=0.25 \mathrm{~s} \) is
along its axis as shown below. The speed of the object is \( 1 \mathrm{~ms}^{-1} \). At \( \mathrm{t}=0 \), the distance of the
object from the mirror is \( 50 \mathrm{~cm} \). The average velocity of theimage formed by the mirror
between time \( t=0 \) and \( t=0.25 \mathrm{~s} \) is
- Azero
- B\( 40 \mathrm{~cm} s^{-1} \)
- Correct answerCinfinity
- D\( 20 \mathrm{~cm} s^{-1} \)
Solution
Focal length $=25 \mathrm{~cm}$
$U_{f}=25 \mathrm{~cm}$
$V_{f}=\infty$
$ < \mathrm{V}>=\frac{V_{f}-V_{i}}{\Delta t}=\infty$
Hence, the correct answer is option: 'C'.