Inside a vessel filled with liquid a converging lens is placed as shown in figure. The lens has focal length $15 \mathrm{~cm}$ when in air and has refractive index $\frac{3}{2}$. If the liquid has refractive index $\frac{9}{5}$, the focal length of lens in liquid is

• A

  $15 \mathrm{~cm}$
• B

  $-60 \mathrm{~cm}$
• C

  $90 \mathrm{~cm}$
• Correct answer
  D

  $-45 \mathrm{~cm}$

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