Question

what is the power of a lens immersed in a liquid of refractive index same as that of lens​

Answer 1

Answer:

The power of a lens in dioptres is the inverse of its focal length. Assuming a thin lens (thin compared to its radius of curvature) the power is given by the approximation:

where R1 and R2 are the radii of curvature of the faces, and n1 and n2 are the refractive indices of the medium and the lens. For equal curvatures the right hand parentheses can be simplified, but since we are looking for a ratio we can eliminate it altogether. Assuming a refractive index of 1 for air, the left hand parentheses evaluates to 0.5 for air, and 0.2 for the liquid. The ratio is therefore 2.5.