A concave lens behaves as a diverging lens, when it is placed in a medium of refractive index less than the refractive index of the material of the lens and behaves as a converging lens, when it is placed in a medium of refractive index greater than the refractive index of the material of the lens. In the given case, concave lens is immersed in a medium having refractive index greater than the refractive index of the material of the lens (1.65 > 1.5). Therefore, it will behave as a converging lens.
