A wire of length $L$, area of cross section $A$ is hanging from a fixed support. The length of the wire changes to $L_1$ when mass $M$ is suspended from its free end. The expression for Young's modulus is:

• A

  $\frac{Mg\left(L_1-L\right)}{AL}$
• B

  $\frac{MgL}{A{L}_1}$
• Correct answer
  C

  $\frac{MgL}{A\left(L_1-L\right)}$
• D

  $\frac{Mg{L}_1}{AL}$

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