Q124 / 180 · NEET 2018 · Physics

An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be

  • A
    30 cm towards the mirror
  • Correct answer
    B
    36 cm away from the mirror
  • C
    30 cm away from the mirror
  • D
    36 cm towards the mirror

Solution

Figure

By mirror formula,v1=ufu-f=-40-15-40+15=600-25=-24 cm 

Figure

When object is displaced by 20 cm towards mirror v2=ufu-f=-20 -15-20+15=-60 cm

Displacement of image =v2-v1=-36 cm

= 36 cm away from the mirror

Hence, the correct answer is option: 'B'.

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