$A$ lens is placed between a source of light and a wall. It forms images of area $A_1$ and $A_2$ on the wall for its two different positions. The area of the source of light is

  • A
    $\sqrt{A_1 A_2}$
  • B
    $\frac{A_1 + A_2}{2}$
  • C
    $(\frac{\sqrt{A_1} + \sqrt{A_2}}{2})^2$
  • D
    None

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