Which of the following lenses will bend the light rays through the largest angle?

The power of a lens is defined as the reciprocal of its focal length (P = 1/f) and represents the degree of convergence or divergence it achieves [1]. A lens with a shorter focal length bends light rays through larger angles, focusing them closer to the optical center [1]. Consequently, a lens with a higher magnitude of power (measured in dioptres) indicates a shorter focal length and a greater ability to bend light [1]. In the given options, the magnitude of power is highest for the lens with +2.5 D (2.5) compared to +2.0 D (2.0), -1.5 D (1.5), and -2.0 D (2.0). While the positive sign indicates a convex (converging) lens and the negative sign indicates a concave (diverging) lens, the bending angle depends on the absolute power [1]. Therefore, the +2.5 D lens bends light through the largest angle.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.8 Power of a Lens > p. 157