A convex lens of refractive index (3)/(2) has a power of 2.5 D in...

Focal length of a convex lens having power $2.5 \mathrm{D},=\frac{1}{2.5} \mathrm{~m}$ Also focal length of a lens in a medium of refractive index $\mu$ is given by $\frac{1}{f}=(\mu-1)$\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$<img src="https://cdn-question-pool.Quantrex.app/pyq/aiims/Pb2mnrvKn_oEWdvcJ-7bkKGe1YWeecOadMiPbp_oDFU.original.fullsize.png"><br> Dividing the two,$2.5 \frac{0.5}{-0.25} \Rightarrow \frac{1}{f^{\prime}}=\frac{-5}{25 \times 0.25}=-1.25 \mathrm{D}