An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is…

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
  1. 30 cm towards the mirror
  2. 36 cm away from the mirror
  3. 30 cm away from the mirror
  4. 36 cm towards the mirror

Solution


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

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

Asked in: NEET 2018

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