An object is mounted on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens placed between these walls. The lens is kept at distance $x$ in front of the second wall. The required focal length of the lens will be

• Correct answer
  A

  $\frac{x}{2}$
• B

  $\frac{x}{4}$
• C

  Less than $\frac{x}{4}$
• D

  More than $\frac{x}{4}$ but less than $\frac{x}{2}$

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