Q16 / 116 · NTA Abhyas (JEE Main) 2020 · Physics · Ray Optics

A point object is kept just beyond the first focus of a convex lens. If the lens starts moving towards the right with a constant velocity, the image will

Figure

  • A
    always move towards right
  • B
    always move towards left
  • C
    first move towards right and then towards left
  • Correct answer
    D
    first move towards left and then towards right

Solution

dv dt = v u 2 × du dt

V image/lens = v u 2 × V object/lens

till u become 2f, m > -1 so Vimagelens> Vobjectlens and the image will move towards left and when

u become > 2f,  Vimage/lens < Vobject/lens and the image will move towards the right.

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

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