The power of a lens is defined as the reciprocal of its focal length, expressed as \(P = \frac 1f\). In this case, the power is \(P = 1.5\ D\). Therefore, the focal length can be calculated as \(f = \frac {1}{1.5}\).
This simplifies to \(f= \frac {10}{15}\), which results in a focal length of \(f = 0.66\ m\). A positive focal length indicates that the lens is convex.
Consequently, the lens is identified as a convex or converging lens.